chroma

Chroma is a term used in color science and everyday description to denote the quality of a color's purity or vividness. Derived from the Greek khroma meaning color, it is distinguishable from hue (the type of color) and lightness or brightness (the perceived luminance). In most color spaces, chroma is quantified as the extent to which a color deviates from a neutral gray of the same lightness. In the CIE L*a*b* and CIE L*u*v* models, chroma can be computed as C* = sqrt(a*^2 + b*^2) (and similarly for uv). In cylindrical representations such as CIELCH or HSL/HSV, chroma corresponds to the saturation component, describing how intense the color is at a given hue and lightness.

In practice, chroma is used to describe how pure a color appears. High chroma colors are vivid and intense; low chroma colors are muted or grayish. Artists and designers manipulate chroma to convey mood, contrast, and depth, often using palettes with varying chroma levels.

In media production, chroma is also associated with chroma keying, a technique for removing a specific color (commonly green or blue) to composite images.

The term is widely used beyond theory, appearing in branding and software as a name or descriptor for color tools, palettes, and graphics utilities. While definitions vary with color model, chroma broadly represents colorfulness relative to brightness.