Reference

Color Format Reference

The formats behind every color picker: what each channel means, how alpha works and how contrast is actually calculated.

The same color, several coordinate systems

Hex and RGB describe the same sRGB channels. HSL and HSV re-coordinate those channels for humans. CMYK is a subtractive print model that depends on ink and paper, and WCAG contrast is a luminance calculation layered on top. Converting between them is arithmetic, not approximation — except where a physical device profile is involved.

Why conversions sometimes disagree

Naive CMYK conversion ignores ink limits and color profiles. Browser rendering applies the display profile. A color that matches numerically can still look different on paper or on a wide-gamut screen. Treat numeric conversions as exact within sRGB and physical matching as a separate problem.

All entries

Hex color#RRGGBB notation, its shorthand forms and the 8-digit alpha variant. RGB colorThree sRGB channels from 0 to 255, plus optional alpha. HSL colorHue in degrees, saturation and lightness in percent. HSV / HSB colorHue, saturation and value — the model behind most color pickers. CMYK colorSubtractive cyan, magenta, yellow and key (black) for print. CSS named colorsAbout 148 keyword colors, from aliceblue to yellowgreen. Alpha channelOpacity from fully transparent to fully opaque, in 0–1 or 0–255. WCAG contrast ratioThe 4.5:1 and 3:1 thresholds for readable text and UI components. Relative luminanceThe WCAG brightness measure behind contrast ratios. sRGB gamutThe default web color space, and what happens outside it.

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