yellowness

Yellowness is the perceptual attribute of color associated with yellow hues. In color science, yellowness is quantified as part of color-space coordinates; for example, in the CIELAB color space the positive b* coordinate indicates increasing yellowness (negative b* indicates blue). A separate index, the yellowness index (YI), is used to quantify yellowing in materials such as plastics, paper, and coatings. YI values are derived from color measurements under standardized lighting and observer conditions and track changes due to aging, heat, or UV exposure.

Natural and applied contexts: Pigments such as carotenoids impart yellow coloration to foods and living tissues, including corn and egg yolk. In plants, yellowing can signal ripening or senescence. In textiles and paints, yellowness often results from chemical aging, photooxidation, or heat treatment, and is a common quality-control parameter.

Health and diagnostics: Yellowing of the skin or eyes, jaundice, arises from elevated bilirubin and can indicate liver, biliary, or hemolytic disorders. The specific hue of yellow can vary with bilirubin level and lighting.

Perception and measurement: Because perceived yellowness depends on illumination and context, objective color measurements are used to supplement subjective assessment. Yellowness is one component of color appearance together with lightness and other hue directions.

See also: color science, jaundice, carotenoids, aging of materials.

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