The system of hexadecimal color definition is used in many areas of computer-aided design. In this system, a color is represented by three consecutive hexadecimal numbers , each of which stands for a color in the RGB color space . RGB is an abbreviation for the proportions of the primary colors red , green and blue in the mixed color . The hexadecimal color definition is usually in six-digit form, i.e. as a string of three hexadecimal numbers, each written in two digits, according to the scheme: which allows different states to be defined per octet (= 256) - from 0 for a completely "switched off" color and 255 (FF) for 100% color saturation . This results in ( , therefore ) different colors. It is the additive color mixture used for mixing the colors; the code results in the color yellow because red is mixed with green.
This type of notation is often used for web colors for the color design of Internet pages.
In addition to the usual 6-digit color values, 3, 9 and 12-digit color values are also possible. The X Window System supports all four options, even if in practice the 9- and 12-digit color value specifications are reduced to 6-digit ones, as hardly any graphics hardware is able to process such color depths.
The colors shown in this article are not binding and may appear different on different display devices.
One possibility to approximately calibrate the display with purely visual means is offered by the adjacent test image (only with native display resolution and when the page is not displayed zoomed):
display device to sRGB mode, if available. If a letter (“R” for red, “G” for green or “B” for blue) appears strongly on one or more of the three gray areas, the gamma correction of the corresponding color channel should be corrected. sRGB corresponds to a gamma value of 2.2, which is the common value for TVs and computers with Windows or macOS (from version 10.6).