KNOWLEDGE MAP · REFERENCE
Find the word. Understand the idea.
From spectra to output transforms: definitions, practical examples and connections. Start with a commonly confused pair, or find the term you need below.
Keep the definition, the test and its limitations together.
Gamut
Which chromaticities and values a basis and range describe. It does not itself specify light encoding.
Find definition ↗Transfer function
How one quantity is represented by another, for example relative linear light by nonlinear code.
Find definition ↗sRGB and Display P3: different primaries, the same sRGB function.
Does changing the function automatically widen gamut?
A comparison of definitions, not an automatic analysis of an uploaded file.
01 / GLOSSARY
The term index
Definition → example → full chapter. Follow each entry’s link to cite it directly.
Shown: 86 / 86
Colour
A perceptual result of a spectral stimulus interacting with an observer and viewing conditions. Colour is not a ready-made RGB property of an object.
The same fabric can look different under two lamps without the material changing.
Light
Optical radiation capable of producing a visual sensation. Colour science cares about its spectral composition, not only total power.
First establish whether the set lighting or only the image processing changed.
Spectrum
A quantity distributed over wavelength or frequency. For light it shows how much energy is present across the visible range.
Do not label a power plot as a material-reflectance spectrum.
SPD
Spectral power distribution: radiant power per unit spectral interval. Its shape describes a source in more detail than one correlated colour temperature.
For two similarly rated LEDs, compare spectra rather than the Kelvin number alone.
Wavelength
A physical property of periodic radiation. One perceived colour need not correspond to one wavelength; most stimuli are polychromatic.
An RGB magenta patch does not require one magenta spectral line.
Illuminant
A standardised or described spectral lighting condition used as a reference condition in colorimetry.
D65 in a profile is not a model of your desk lamp's spectrum.
Reflectance
The fraction of incident radiation reflected by a surface. Spectral reflectance combined with the illuminant forms the spectrum reaching an observer or camera.
In a simple model, multiply illumination by spectral reflectance wavelength by wavelength.
Metamerism
Different spectral stimuli having matching tristimulus values for a specified observer and conditions. Changing illuminant or observer may break that match.
Recheck matching samples under a second illuminant while keeping camera and observer fixed.
Tristimulus values
Three values describing a colour match in a defined three-component colorimetric system such as CIE XYZ.
Identical XYZ does not identify a unique SPD.
Standard observer
A standardised model of human colour matching used by CIE for XYZ and chromaticity calculations; it is not a profile of one individual.
When comparing values, check whether they use a 2° or 10° observer.
S/M/L cones
Three cone classes with overlapping spectral sensitivities in short-, medium- and long-wavelength regions. They are not literal B/G/R sensors.
Do not label S/M/L curves as screen B/G/R spectra without distinguishing them.
Visual adaptation
A change in the visual system in response to surrounding illumination and brightness, making perception of a stimulus context-dependent.
Compare a neutral patch after a bright coloured screen and after a neutral surround.
Luminance, Y
Photometric luminance in a specified direction, measured in cd/m². CIE Y is proportional to it under an appropriate normalisation; relative Y alone is not a number of nits.
Y=0.18 relative to white does not give cd/m² without a scale.
Brightness
A perceptual attribute describing how much light an area appears to emit. It is not identical to physical luminance.
Two identical patches on different surrounds may appear different in brightness.
Lightness
A relative perceptual attribute of how light an object appears compared with a similarly illuminated white reference. It is not a synonym for brightness or code value.
White paper in shade and a bright highlight are not the same lightness-description task.
Hue
The colour-appearance attribute by which an area is perceived as reddish, yellowish, greenish, bluish or a combination of these.
Judge skin hue with the lighting known, not merely a scope-trace direction.
Saturation
Perceived colourfulness relative to brightness; it depends on viewing conditions and is not simply RGB distance from grey.
A slider value of 50 in two applications is not an equal physical saturation.
Chroma
Perceived colourfulness relative to the brightness of a similarly illuminated reference area. In interfaces, Chroma can also refer to Cb/Cr, which is a different technical meaning.
In codec documentation, Chroma often means Cb/Cr rather than the perceptual attribute.
Chromaticity
Colour coordinates independent of an overall luminance scale. For example x=X/(X+Y+Z), y=Y/(X+Y+Z); this normalisation is undefined for a zero stimulus.
Multiplying nonzero XYZ by 2 leaves xy unchanged.
CIE XYZ
A CIE tristimulus colorimetric system. XYZ describes colour matching for a specified observer and normalisation, not a spectrum or complete appearance under all viewing conditions.
Fix observer, white point and normalisation before comparing XYZ.
White point
The achromatic reference chromaticity a system treats as neutral white. Rec.709, sRGB, Display P3 and Rec.2020 normally use D65.
A space's D65 white and a camera's 6500 K balance are not interchangeable settings.
D65
A CIE standard daylight reference widely used as the white point of television and computer RGB systems.
Equal R=G=B gives the reference neutral only in a known representation and path.
CCT
Correlated colour temperature: the temperature of a Planckian radiator whose chromaticity is closest to the stimulus under a defined rule. It does not describe the source's full spectrum.
Do not choose an RGB input space from the lamp's colour temperature.
RGB
An additive three-component coordinate model. R/G/B values acquire colour meaning only after primaries, white point and encoding/transfer context are defined.
The triplet 0.5/0.5/0.5 requires knowing whether it is linear or encoded.
Primaries
Reference primaries of a coordinate system, which can be physically realisable or mathematically specified. An xy triangle does not describe the entire three-dimensional colour volume.
sRGB and Display P3 have different primaries but the same transfer function.
Colour space
A defined coordinate system and rules that connect numbers to colour meaning. RGB systems normally require primaries, a white point and transfer/encoding context.
Record primaries, transfer, Y′CbCr matrix and range instead of only a filename.
Gamut
The set of colours a system or device can represent under defined constraints. Gamut is part of a colour space, not a complete synonym for it.
Moving sRGB into a wider container does not create new source colours.
Working space
The colour representation in which primary processing and grading operations are performed. It is chosen so transforms and tools behave predictably.
Check the LUT's input representation even in a managed project.
Transfer function
A mathematical relationship between a physical/scene quantity and a signal, or between a signal and display light. OETF, EOTF, OOTF, log, PQ and HLG describe different parts of the chain.
State the direction and units on both sides of a formula.
OETF
The relationship between scene light or a camera exposure-like quantity and an encoded electrical/digital signal in a camera-side model.
BT.709 OETF describes source encoding; do not automatically call it BT.1886.
EOTF
The relationship from an encoded display signal to physical display light. PQ/ST 2084 is an EOTF.
A PQ code has a reference absolute meaning, but a TV may map it to its capability.
OOTF
The overall system relationship from scene light to display light, including rendering intent/system contrast rather than only one file encoding.
Interpret the same relative HLG signal together with system gamma.
Gamma
A power-law or approximately power-law class of transfer relationships. Interfaces often use Gamma more broadly for any transfer preset, which is technically imprecise.
Record sRGB, BT.1886 or the exact log name rather than just Gamma.
Log
A family of nonlinear encodings with logarithmic regions for capture or working data. The curve, range and required precision are specification-dependent; Log is not a finished look.
Do not automatically carry LogC3 settings and precision assumptions into LogC4.
Matrix transform
A linear coordinate transform, for example between linear RGB spaces with different primaries. It does not automatically perform tone mapping or complex gamut compression.
Apply an RGB basis change after the necessary transfer decoding.
Chromatic adaptation transform
A model for transforming colour coordinates between different adopted/reference white conditions, approximating part of visual adaptation.
For D65→D50, check direction and avoid a duplicate adaptation.
Scene-referred
A state in which values retain a relationship to the scene/exposure before final display rendering. Scene-referred does not necessarily mean linear.
ACEScct is nonlinear but is not yet an ordinary display image.
Scene-linear
A scene-referred representation in which numeric values are proportional to a chosen linear light/exposure quantity. Important for physically meaningful compositing.
For physically meaningful mixing, also check straight/premultiplied alpha.
Display-referred / output-referred
A state after colour rendering, oriented to the characteristics of a target display and viewing environment.
Do not blindly process a finished logo as flat camera log.
Tone mapping
Redistribution of luminance/tone relationships to fit source dynamic range into a target display without simple hard clipping.
Inspect highlight detail and nearby contrast, not only the maximum value.
Gamut mapping
Mapping between available gamuts or colour volumes with chosen compromises. It need not affect only already out-of-gamut colours and cannot guarantee every appearance attribute.
Check hues and gradients after mapping, not only whether RGB fits 0…1.
DRT
A rendering stage that turns a scene-referred representation into a display-oriented image; it can combine tone scale, gamut mapping and other perceptual decisions.
Establish whether rendering is performed by the project or your explicit node.
RAW
A family of formats retaining early camera data and interpretation parameters. It does not promise untouched linear sensor samples: BRAW, for example, uses partial demosaic and nonlinear coding.
The RAW label does not prove the data is uncompressed or unprocessed.
Debayer / demosaic
Reconstruction of full-colour data from a colour-filter-array mosaic. Debayer refers to a Bayer pattern; demosaic is the broader term.
Compare decoders with white balance and exposure held equal.
Camera gamut
A camera RGB representation after specified sensor processing. Its encoding primaries must not be equated with the spectral sensitivities of the sensor filters.
For ARRI or Sony, identify the recording-mode curve/gamut pair, not its appearance.
Camera Log
A nonlinear transfer encoding from a specific camera family, such as LogC or S-Log. It must be interpreted together with the matching gamut/generation.
The instruction 'shoot log' is insufficient for reproducible interchange.
White balance
A camera-side adjustment/interpretation that changes relative channel gains or an equivalent transform so a chosen neutral stimulus becomes neutral.
Changing balance cannot restore texture in a clipped sensor channel.
Y′CbCr
A luma/colour-difference representation. Common NCL matrices derive Y′ from nonlinear R′G′B′; interpretation also needs primaries, transfer, matrix and range. It is not a gamut.
Check matrix and range before trying to grade away an unexpected hue.
Luma, Y′
A signal component formed by weighting nonlinear R′G′B′ in common NCL models. It is not linear CIE Y or perceived lightness.
A grey ramp poorly exposes an NCL-matrix mismatch: weights sum to one.
Cb / Cr
Colour-difference components related to blue and red deviations from Y′. Neutral is zero before integer coding and a specified centre code after range offset.
For 10-bit narrow range, neutral Cb/Cr is 512, not 64.
Matrix coefficients
Weights for building luma and colour-difference components. BT.601, BT.709 and BT.2020 NCL differ; changing the matrix alone is not an RGB gamut conversion.
Test 601 versus 709 on coloured samples, not only neutrals.
Full range
Mapping nominal signals across a full integer range according to specified rules. Luma commonly uses 0…2ⁿ−1; colour-difference component rules must be checked separately.
Code 64 in 10-bit full range is not nominal black.
Video / limited / narrow range
Nominal coding with separate reference anchors. For 10-bit Y′: black 64, white 940; Cb/Cr: 64…960 with neutral 512. Headroom does not make every interface code valid.
940 in 10-bit narrow Y′ is nominal white, not the limit of all allowed data.
Bit depth
Bits per sample. An unsigned n-bit integer has 2ⁿ possible bit patterns; nominal levels depend on range. Floating-point precision additionally depends on its exponent and significand.
An 8-bit source placed in a 10-bit container does not gain 10-bit capture precision.
Quantisation
Mapping a continuous or more precise quantity to a discrete set of code values. Steps that are too coarse can appear as banding.
Inspect a smooth gradient after the intended processing, not just at input.
Chroma subsampling
Reduction of the spatial sampling rate of Cb/Cr relative to luma. 4:4:4, 4:2:2 and 4:2:0 describe sampling geometry, not bit depth.
Do not infer 4:2:2 merely from a 10-bit file.
4:4:4
Luma and chroma are represented on the full spatial sampling grid with no chroma subsampling.
Check pixel format and codec: 4:4:4 alone does not mean lossless RGB.
4:2:2
Chroma has roughly half the horizontal sampling density while retaining vertical density relative to luma.
Fine coloured text can lose horizontal chroma detail.
4:2:0
In a typical progressive representation, chroma sampling density is roughly half that of luma horizontally and vertically.
A simple progressive 2×2 block has one Cb and one Cr sample but four Y′ samples.
Chroma siting
The phase/spatial position of chroma samples relative to the luma grid. A 4:2:0 label alone does not fully define siting.
A shifted coloured edge can arise from chroma-location interpretation.
Codec
A method for encoding/decoding an image. A codec defines compression and representation details but does not replace primaries, transfer, matrix and range signalling.
MOV can contain different codecs and colour representations.
Colour metadata / tags
Signalling fields telling a player/decoder how to interpret primaries, transfer, matrix, range and other properties. Tags do not transform pixel values by themselves.
Read ffprobe fields first; do not replace unknown with a guess of 'probably 709'.
SDR
A class of display/rendering workflows using traditional luminance ranges, commonly associated with Rec.709/BT.1886-style video viewing. SDR is not a synonym for 8-bit.
10-bit SDR remains SDR without a change of display system.
HDR
A capture/render/display system capable of reproducing a wider luminance range and often a wider colour volume. HDR requires a defined transfer/rendering context, not merely a brighter monitor.
Rec.2020 primaries do not prove PQ or HLG encoding.
Nit / cd/m²
A unit of luminance: 1 nit equals 1 candela per square metre. Used for display luminance, reference white and mastering/display peaks.
512 is a code; 203 cd/m² is luminance. A specified function connects them.
PQ / ST 2084
Perceptual Quantizer — an absolute HDR EOTF mapping signal values to defined display luminance values up to a mathematical ceiling of 10,000 cd/m².
A 1000 cd/m² master need not use the entire PQ range up to one.
HLG
An HDR system with a relative OETF combining square-root and logarithmic regions. Display behaviour also depends on OOTF, system gamma and display characteristics.
75% HLG is about 203 cd/m² only under specified conditions, including a 1000 cd/m² display and gamma 1.2.
HDR reference white
A working reference luminance for diffuse/graphics white in HDR production. ITU BT.2408 commonly uses a nominal HDR reference white around 203 cd/m².
Do not place every highlight and logo at one level merely because of a table value.
Mastering display
The reference display on which a master is evaluated and approved; its black, peak and gamut capabilities are part of the mastering context.
Record display peak and maximum content light level separately.
MaxCLL
HDR content metadata for maximum content light level in cd/m² under the applicable analysis procedure. It is not mastering-display peak or a substitute for inspecting the file.
After a substantial master change, recheck whether analysis metadata is current.
MaxFALL
HDR content metadata for the maximum frame-average light level across a programme. It is not MaxCLL, whole-film average or a measurement of the current TV.
The brightest frame's average is not its peak pixel.
Colour volume
The three-dimensional region of available colours including chromaticity and luminance. A 2D gamut triangle alone does not fully describe an HDR display.
A saturated colour may face different limits at mid-level and near peak.
Input Transform
A technical transform that maps a known source state into a chosen working/common representation. Incorrect source interpretation breaks the rest of the chain.
One shared Input for different cameras requires matching actual representations.
Output Transform
A transform/rendering stage that maps the working/scene state to a target display/output state. It can include tone/gamut rendering, not only matrix + gamma.
After changing SDR/HDR target, recheck rendering, encoding and viewing.
CST
Resolve OFX for explicit Input Colour Space/Gamma → Output Colour Space/Gamma conversion with optional tone/gamut mapping controls.
A CST node does not prove its Input Color Space and Input Gamma are correct.
RCM
DaVinci Resolve's project-level managed colour pipeline: source tagging/input transforms, timeline working state and output rendering are managed by the project system.
Before adding an Output CST, establish what RCM already performs.
LUT
A tabulated mapping from input values to output values. A LUT can be technical or creative but always assumes a specific input/output state and does not infer context automatically.
A .cube without input/output documentation is not a reproducible interchange contract.
ACES
A standardised colour-management and interchange architecture from the Academy using common scene-referred representations and defined Input/Look/Output transforms.
Record the version and Output Transform, not only the ACES project label.
AP0
The very wide ACES primary set used by the ACES2065-1 archival/interchange representation.
Do not judge intermediate AP0 values directly as ordinary screen RGB.
AP1
A more compact ACES primary set used by working encodings including ACEScg and ACEScct.
ACEScg and ACEScct use AP1 but encode the same signal with different numbers.
ACEScct
An AP1-based scene-referred ACES grading encoding with a toe near black, designed for colour grading.
Do not confuse the toe segment with the whole of ACEScct being linear.
DaVinci Wide Gamut
Blackmagic Design's wide RGB working gamut for Resolve, commonly paired with DaVinci Intermediate in scene-referred RCM/CST workflows.
Specify DWG and DaVinci Intermediate separately in settings.
DaVinci Intermediate
Blackmagic Design's log-like scene-referred transfer function intended to pair with DaVinci Wide Gamut as a wide working state.
The Intermediate curve is not defined by the area of a gamut triangle.
Colour Management
Organisation of known input, working and output representations and transforms. It helps reconcile a path but does not guarantee identical physical results on arbitrary displays.
Even with matching setting names, check transform versions.
Display calibration
Adjustment toward a measurable target within device capabilities, followed by verification. Profiling describes behaviour; calibration does not enlarge a panel’s physical gamut.
A measurement report matters more than assuming a profile makes any screen a reference.
Reference monitoring
A controlled display path with a known output transform, signal path and calibrated reference display on which colour decisions are made.
Compare the same frame, output mode and display state.
TOPIC ILLUSTRATIONTHE ESSENTIAL IDEA
Colour-science glossary
A useful definition answers three questions: what it describes, where it belongs in processing and what it cannot establish. Each term therefore includes an example and a route into a longer chapter.
- Separate a physical quantity from a code and a visual impression.
- Read definitions with their conditions, not as universal recipes.
- Turn a short definition into a testable working explanation.
How to use a definition
Start with the term and its object. If someone says “brightness”, ask whether they mean perception, a photometric quantity, Y′ in video or an application control. Similar names do not establish an identical quantity.
Search includes Russian and English names, abbreviations, definitions and examples. A category narrows the index, not the meaning. A term link reveals its target even after filtering; sources and longer chapters provide context.
What this means in practice
Search “luma”, then compare it with Luminance. The former concerns nonlinear signal components; the latter needs a photometric meaning and units, or an explicitly relative normalisation.
Which layer the term belongs to
It is useful to separate physical light and material, colour measurement, numerical image representation and display. These layers are connected, but not interchangeable. A code change can preserve colour coordinates; the same code under a different interpretation can describe another stimulus.
A colour matrix operates on specified coordinates. A transfer function describes a different relationship. Viewing conditions add another layer: matching digital values do not prove matching appearance in different surrounds.
What this means in practice
“The file was recoloured” is ambiguous. Ask whether decoded values, the space description, the output transform or only the application view changed.
Similar words, different tasks
Gamut is not a transfer function. Log is not RAW. Scene-referred does not necessarily mean scene-linear: ACEScct is nonlinear but still describes the scene. Assigning a space is not transforming coordinates between spaces.
Test the distinction operationally: what should remain unchanged? When converting between compatible colourimetric representations without gamut limiting, the described colour is preserved while coordinates can change. Merely assigning a new meaning can retain the numbers but change the colour.
What this means in practice
In the colour-space lab, compare assignment and conversion. Check XYZ before display-preview clipping, not just the swatches.
A complete description, not one label
For reproducible exchange, specify primaries and white point, transfer function, component representation, range, bit depth and purpose. Y′CbCr also requires matrix and chroma-sample location. Files can omit fields or carry incorrect ones.
“Rec.709, 10-bit” does not locate rendering, explain range interpretation, identify a separate monitoring LUT or define the output. Missing conditions come from camera documentation, processing settings and an agreed test, not from the filename extension.
What this means in practice
For a VFX handoff, also state straight/premultiplied alpha and the expected working representation. A codec name alone cannot establish either.
Subscripts, primes and units matter
Y, Y′ and a Y′ integer code are not three notations for the same number. A prime often identifies a nonlinear representation; integer coding additionally depends on scale and rounding. A nit equals cd/m², but normalised RGB or relative Y needs a physical scale before it can express display luminance.
A negative computational RGB value is not necessarily an error. It can result from a basis conversion. Before clamping it to zero, determine whether it is intermediate data and where target-gamut mapping belongs.
What this means in practice
Code 512 in 10-bit Video Cb/Cr represents neutral chroma. The same code in Y′ describes a different component and a different normalised level.
Taking a term into Resolve
An application control is not always identical to a scientific definition. Gamma in Primaries is a grading control; Gamma in an input/output description identifies signal interpretation. Color Space Transform is an operation with specific input and output settings, not a universal fix.
Before acting, locate the owner of technical processing: project settings, RAW decoding, nodes, LUTs or a separate view. Do not add a second input or output transform simply because another tutorial uses one.
What this means in practice
Write the chain for one clip: decoding → input → working grade → output → view. Under each stage, record the exact setting location in your project.
DO. OBSERVE. EXPLAIN.
Turn a word into an exact description
Open a project or use a synthetic example. Record assumptions without altering source media.
- 01
Find an ambiguous word
Choose “brightness”, “gamma” or “profile” from a discussion and identify the intended object.
CHECKThe quantity, stage and known evidence are named; unknowns are explicit.
- 02
Compare a neighbouring concept
Find two related terms and explain the difference through an operation, not merely a paraphrase.
CHECKThe example states what stays fixed and what changes.
- 03
Describe the chain
For a clip, record input, working representation and output, plus the separate viewing path.
CHECKNo profile was inferred from the file extension alone.
- 04
Check the source
Open the primary source behind a disputed definition. Save the term’s direct link for a colleague.
CHECKThe link opens the intended entry and the explanation retains its conditions.
Check your understanding
TEST THE EXPLANATION
A situation, not a trick question.
Answer first. Open the reasoning afterwards.
01Does matching RGB mean matching colour?+
Only with matched definitions and conditions. The numbers need a known basis and encoding; appearance also depends on viewing and surround.
02ACEScct is nonlinear. Is it therefore display-referred?+
No. Nonlinear scene encoding is not an output rendering. Encoding and image role are different properties.
03A conversion produced negative RGB. Clamp it immediately?+
First establish the basis and stage. Such values can be valid in an intermediate representation; clipping changes the signal and is not a substitute for deliberate gamut mapping.
Avoid these shortcuts
- Do not replace missing information with familiar settings.
- Keep the conditions with the number or definition.
From the model to your workflow.
Record the Resolve version, colour-management mode, input interpretation and viewing conditions. This reference helps define a check, but does not replace reviewing the full shot or validating a delivery file.
CHECK THE FOUNDATION
Sources and model limits.
Editorial review: 1 October 2026. Links identify the definitions and formulas; exercises are independent teaching examples.
- [1]CIE · e-ILV ↗
Working definitions; site explanations are not verbatim standard quotations.
- [2]CIE · Perceived colour ↗
Perceived colour, surround and adaptation.
- [3]CIE · Observer metamerism ↗
Matching tristimulus values for different spectra; observing conditions.
- [4]ICC · sRGB ↗
Primaries, D65 and the piecewise transfer function.
- [5]ICC · Display P3 ↗
P3, D65 and the sRGB function.
- [7]ITU-R · BT.709-6 ↗
Sections 1, 3, 4: primaries, OETF, coefficients and 8/10-bit digital levels.
- [8]ITU-R · BT.1886 ↗
Annex 1: EOTF depending on black and white luminance.
- [9]ITU-R · BT.2100-3 ↗
PQ, HLG; Table 9: 10/12-bit integer representation.
- [10]ITU-R · BT.2408-9 (03/2026) ↗
HDR reference white and conditions for 75% HLG corresponding to about 203 cd/m².
- [11]ITU-T · H.273 (07/2024) ↗
Independent video-identification fields; metadata is not a transform.
- [12]ACES · White point ↗
x=0.32168, y=0.33767; D60-like is not exact CIE D60.
- [13]ACES · ACEScct ↗
AP1 and nonlinear scene encoding with a linear toe.
- [14]ACES · Output Transforms ↗
Target-display rendering and encoding; not merely a tag change.
- [15]Blackmagic · DWG / Intermediate v1.1 ↗
DWG and Intermediate specify distinct properties of a working representation.
- [16]Blackmagic · Color ↗
CST, RCM and Color tools. Menu details depend on the Resolve version.
- [17]Blackmagic · RAW ↗
Partial demosaic and nonlinear 12-bit BRAW coding; do not generalise to all RAW.
- [18]ARRI · LogC4 specification ↗
Precision is format-specific: LogC4 specifies a 12-bit minimum; 10 bits is not universal.
- [19]FFmpeg · ffprobe ↗
Read stream fields without modifying the file; unknown does not prove a particular colour space.
- [20]FFmpeg · Content light metadata ↗
MaxCLL and MaxFALL are different content-metadata fields, not measurements of the current display.
- [21]OpenColorIO · Displays & Views ↗
Working data and viewing transforms are distinct.
- [22]W3C · CSS Color 4 ↗
RGB conversions and browser colour definitions; document status is stated in the specification.