Short answer
RGB describes a colour as amounts of three coloured lights — red, green and blue — added together, which is how every screen and camera sensor works. But 'red', 'green' and 'blue' are only defined once you choose an RGB space: sRGB, Display P3, Adobe RGB and Rec. 2020 each put their primaries somewhere different, so the same triple such as (0, 255, 0) names a different green in each.
Convert any colour into this system with the colour converter
RGB is an additive model: starting from black, light from three primaries is added. Full red plus full green gives yellow, green plus blue gives cyan, all three give white, and intermediate amounts give everything in between. Three primaries suffice because human colour vision has three cone types; any colour a display shows is a match, in cone responses, for the colour it is imitating, not a copy of its spectrum. The consequence is that no three real primaries can match every visible colour: the gamut of an RGB space is the triangle its primaries span on a chromaticity diagram, and colours outside it are unreachable with positive amounts of light.
To turn RGB numbers into a definite colour you need the chromaticity of each primary, the chromaticity of white (which fixes the relative strength of the primaries), a transfer function linking the numbers to light, and the range of values. sRGB, Display P3, Adobe RGB (1998) and Rec. 2020 share the D65 white but differ in primaries and curves. The table on this page takes the same instruction — full red, full green — and shows, in OKLCH terms, what it means in each space. The greens differ most: Rec. 2020's green has far more chroma than sRGB's and a different hue angle.
Because most RGB spaces store gamma-encoded values, the numbers are neither proportional to light nor to perceived lightness. The three channels also contribute very unequally to luminance: in sRGB, green carries about 72% of the luminance of white, red about 21% and blue about 7%. So a numerically 'balanced' RGB palette is visually unbalanced, and differences computed as distances between RGB triples tell you little about how different two colours look. RGB is the right model for storage and display, and the wrong one for judging, comparing or generating colours; that is the job of perceptual spaces such as CIELAB and OKLab.
In 8-bit-per-channel files and in CSS, each channel runs from 0 to 255, giving about 16.7 million combinations. That count is often quoted as the number of colours a screen shows, but many neighbouring combinations are indistinguishable and the set is limited to one gamut. Higher bit depths (10, 12 or 16 bits per channel, or floating point) divide the same gamut more finely, which matters for gradients, heavy editing and wide-gamut or HDR content. Floating-point RGB also allows values below 0 and above 1, which is how some systems represent colours outside the nominal gamut.
| RGB space | Red (1, 0, 0) | Green (0, 1, 0) |
|---|---|---|
| sRGB | L 0.628, C 0.258, h 29.2° | L 0.866, C 0.295, h 142.5° |
| Display P3 | L 0.649, C 0.299, h 29.0° | L 0.849, C 0.369, h 145.6° |
| Adobe RGB (1998) | L 0.702, C 0.288, h 29.2° | L 0.815, C 0.395, h 151.6° |
| Rec. 2020 | L 0.687, C 0.365, h 24.2° | L 0.830, C 0.468, h 152.6° |
Why: One app works in Display P3 and the other in sRGB; the RGB numbers were copied, not converted.
Fix: Copy colours with their colour space, or convert explicitly.
Why: RGB steps are neither light-linear nor perceptually even.
Fix: Space palettes in OKLCH or CIELAB and convert to RGB at the end.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
StandardStrong evidence
sRGB, Display P3, Adobe RGB (1998) and Rec. 2020 all use a D65 white point but specify different red, green and blue primary chromaticities.
Source: CSS Color Module Level 4; ITU-R Recommendations BT.709, BT.2020 and BT.2100
StandardStrong evidence
In sRGB, the relative luminance of a colour is 0.2126 × red + 0.7152 × green + 0.0722 × blue, computed on linear-light channel values.
Source: Web Content Accessibility Guidelines (WCAG) 2.2; International Electrotechnical Commission (IEC) webstore and catalogue
Colourwise analysisStrong evidence
The full-green primary of Rec. 2020 has markedly higher OKLCH chroma than the sRGB green primary, so identical RGB triples name visibly different colours in the two spaces.
Based on: Computed by Colourwise from each space's published primaries and white point; see the table on this page.
Source: ITU-R Recommendations BT.709, BT.2020 and BT.2100; International Electrotechnical Commission (IEC) webstore and catalogue; A perceptual color space for image processing (Oklab)
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.