Digital colour is fundamentally different from physical, pigment-based colour — screens create colour by emitting light in varying combinations of red, green and blue, while print and paint work by absorbing and reflecting light, which is why the same colour code can look different on a screen and in print.
Digital displays create colour using the RGB (red, green, blue) additive colour model, combining light rather than absorbing it — a fundamentally different physical process from the subtractive, pigment-based mixing used in paint and print.
Modern use
The CSS Color Module and related web standards define how colour is specified and rendered consistently across web browsers and devices, though actual on-screen appearance still varies by display calibration.
Modern use
Because a colour code (like a HEX value) only specifies a mathematical target, not a guaranteed visual result, the same code can appear noticeably different across uncalibrated screens, and will not exactly match a printed or painted version of the same nominal colour.
Modern use
Three numbers for red, green and blue describe a colour only once it is agreed which red, green and blue are meant, what counts as white, and how the numbers relate to light output. In the mid-1990s there was no such agreement between devices. The sRGB proposal supplied one by describing a typical display of its day, a calibrated cathode-ray-tube monitor, and declaring that to be the default. The alternative approach, embedding a profile that describes each device, was already being standardised by a consortium of vendors. The web ended up using both: a default for untagged colour, and explicit colour spaces for everything else. 1, 2
| When | Where | What happened | Sources |
|---|---|---|---|
| 1978 | SIGGRAPH, United States | Two papers in the same conference proceedings defined the hue-based rearrangements of RGB still offered by colour pickers: Alvy Ray Smith's HSV, and the double-cone model by Joblove and Greenberg that HSL follows. | 3, 4 |
| 1993 | — | The International Color Consortium was established by eight industry vendors to create an open, cross-platform colour management architecture. | 2 |
| 5 November 1996 | — | Authors from Hewlett-Packard and Microsoft published version 1.10 of 'A Standard Default Color Space for the Internet — sRGB'; it was later standardised as IEC 61966-2-1. | 1 |
| Late 2015 to 2016 | — | Wide-gamut screens reached ordinary buyers in Apple's Retina iMac and iPad Pro; the WebKit team wrote in July 2016 that their Display P3 space was about 25% wider than sRGB. | 5 |
| 2020 | — | Björn Ottosson published Oklab, a perceptual colour space fitted to existing colour-appearance data, which CSS later adopted. | 6, 7 |
Claim: A HEX code identifies one exact colour.
Evidence: Only within a stated colour space. On the web a HEX value is read as sRGB, and the CSS specification shows the same measured colour needing different numbers in sRGB, Display P3 and Adobe RGB. Even then the code fixes a target, not what an uncalibrated screen will actually emit. 7, 1
Historical claims above are scoped to a specific period, region or culture where relevant — none are presented as a single universal fact. See methodology.