Color Glossary

A color's identity — red, orange, yellow, green… distributed by angle around the color wheel (0° red, 120° green, 240° blue). What people mean by 'what color' is hue.

How light or dark a color is, from pure black to pure white. Same hue, whiter is lighter, blacker is darker; lightness decides readability and contrast.

A color's intensity — 0% is gray, 100% is pure hue. High saturation grabs attention but also fatigues; UIs usually reserve it for key actions.

Pure hue plus white is a tint, plus black a shade, plus gray a tone. Brand color scales are controlled tint/shade sequences.

Warmth of light in Kelvin: low K skews orange (warm), high K skews blue (cool). A screen's warm mode simply lowers its temperature.

Luminance ratio between foreground and background, 1:1 to 21:1. WCAG requires ≥ 4.5:1 for body and ≥ 3:1 for large text — the hard floor of accessibility.

The WCAG 3 candidate contrast algorithm. It weighs font size, weight and polarity, and reads dark-mode and low-contrast text more accurately than WCAG 2.1.

A coordinate system for color. sRGB is the web default, Display P3 covers more, OKLCH organizes color by human perception.

The full range a device or space can display. Neon-high-saturation colors often fall outside sRGB — the screen can only show its nearest approximation.

#RRGGBB six-digit notation; 24-bit color (about 16.7 million colors) is the web's color space itself.

Additive red-green-blue model, 0-255 per channel. The way screens emit light makes RGB the native model of the digital world.

Subtractive cyan-magenta-yellow-black model, the language of print. Screen RGB to CMYK is only a theoretical approximation — proof against physical swatches.

Hue/saturation/lightness cylinder, more intuitive than RGB. Its flaw is non-uniformity: at 50% lightness yellow looks far brighter than blue.

The new perceptually-uniform space: same lightness value means same perceived lightness, interpolation never grays out — the new standard for design-system scales. Native CSS support.

Numeric change proportional to perceived change. In a uniform space a difference of 10 looks equally different everywhere — the basis of CIEDE2000 and OKLCH.

The CIE's color-difference formula. ΔE expresses perceived distance: under 1 is nearly invisible, under 5 reads as 'the same color', over 10 is clearly different.

The global spot-color system, the lingua franca of print and fashion. Each code has its own ink recipe; screen rendering is a simulation.

The German national standard color system, the benchmark for industrial coatings and powder spraying — RAL 3020 traffic red, for example.

The Swedish system describing color by blackness, chromaticness and hue; common in architecture and interiors.

A century-old system organized by hue, value and chroma; still the official standard for soil and agricultural grading.

Palettes usable by color-vision-deficient users (about 8% of men): never encode by color alone, hold contrast, verify with simulation.

Colors named by purpose, not hue: primary/success/warning/danger. Semantics make theming and dark mode possible.

The most recognizable color of a brand or interface, carrying main actions and emphasis. Usually under 10% of the surface — large use dilutes its pull.

The contrast point beyond the primary: tiny usage (<5%) with maximal hue or saturation opposition — notification dots, CTA buttons.

The gray scale: backgrounds, dividers, body and secondary text all live on it. A neutral's warm or cool bias sets the whole interface's character.

A brand color expanded by lightness into 11 steps (50-950), the staple of design systems — hover, borders and dark mode all get in-family colors.

Colors 180° apart on the wheel (red-green, blue-orange). Together they intensify each other — great for accents, fights itself at 1:1.

Two to four neighboring hues (blue, blue-green, green). Harmonious and safe but flat — one complementary accent breaks the calm.