The complete range of colours a particular device, ink set or colour space can produce or describe.
For an RGB space, the gamut is bounded by its three primaries: every colour it can encode is a mix of them. It is usually drawn as a triangle on a chromaticity diagram, though a true gamut is a three-dimensional solid that narrows towards black and white.
A bigger gamut is not automatically better. Content made for sRGB shown unconverted on a wide-gamut screen looks oversaturated, not more accurate.
A vivid screen green can sit inside Display P3 but outside sRGB, and outside the gamut of CMYK printing entirely.
Almost every 'it looked different on…' problem between screens, or between screen and print, is a colour meeting a smaller gamut and being moved to fit.
A display's gamut is found by measuring the chromaticity of its three primaries, and is often summarised as the area of their triangle on a chromaticity diagram or as a percentage coverage of a standard space. On the more uniform u′v′ diagram, Display P3's triangle is about a quarter larger than sRGB's. A printing gamut is measured from a printed chart of ink combinations and has no simple shape. Area figures are a rough guide in both cases, because a gamut is a volume: how much chroma is available depends on lightness as well as hue.
| Colour space | Largest chroma that fits | Holds oklch(0.7 0.25 145)? |
|---|---|---|
| sRGB | 0.220 | No |
| Display P3 | 0.299 | Yes |
| Adobe RGB (1998) | 0.278 | Yes |
| Rec. 2020 | 0.312 | Yes |
At this lightness and hue sRGB runs out at a chroma of 0.220 and Display P3 at 0.299. A green of chroma 0.25 therefore fits Display P3, Adobe RGB (0.278) and Rec. 2020 (0.312) but not sRGB. On an sRGB screen that colour is shown as something near chroma 0.220: the number in the stylesheet and the colour on the glass part company.
How this was calculated: The boundary is found by bisection: chroma is raised until one linear RGB channel of the space leaves the 0 to 1 range.
A logo is designed in a vivid green or orange on a wide-gamut laptop.
Most other screens clip it to the sRGB edge, and coated offset printing clips it further. Choosing the colour inside the smallest gamut it must survive in, then enriching it where the medium allows, keeps the brand recognisable.
A gradient runs between two colours that are both in gamut.
The path between them can leave the gamut in the middle, depending on the space the interpolation is done in, and the clipped section shows as a flat band. Checking the midpoint as well as the ends catches it.