Fig. 1.

CIELAB or L*a*b* color space with a graphical representation of $\mathrm{\Delta }E$. A device-independent, three-dimensional color space that is intended to be perceptually uniform relative to human color vision, such that a given numerical change is correlated to a perception of change in color. L*a*b* values are correlated to lightness, chroma, and hue, where L* ranges between 0 (black) and 100 (white), a* describes the red–green axis, and b* describes the blue–yellow axis, akin to the opponent pair of the human visual system. The distance between a pair of colors is reported at the color difference $\mathrm{\Delta }E$. CIELAB and $\mathrm{\Delta }E$ were developed by the Commission Internationale de l’Eclairage (CIE) with the intent of measuring the Euclidean distance within a given color space. Intended to be a difference calculator, $\mathrm{\Delta }E$ of 1 represents the smallest noticeable change in color. $\mathrm{\Delta }E$ is illuminant dependent; a change under differing illuminants illustrates a metamerism index, and two colors that appear the same under differing illuminant sources are considered metamers.