CMC is not a color space but a color tolerance equation based on CIELch. It is not a color difference. There is a need to distinguish between the two. Color differences deal primarily with perceptibility of differences, while color tolerances deal with acceptability of differences.

CMC, as a single number tolerance, can be used as a "Go – No Go" gage. CMC is one of the newest mathematical derivations of CIELab Lch data. Years of worldwide study have helped to establish the nonlinear relationship between perceived lightness, hue and chroma in different parts of color space. The result is the CMC equation, which takes into account these nonlinear relationships and weighs each according to its location in that color solid called color space. In CMC, a Delta E of 1.0 represents a consistent color difference, regardless of what area of color space the target and sample are in. This permits the use of a single number for acceptance or rejection decisions. After establishing a CMC color tolerance, the acceptable versus not acceptable decision can be made with much higher confidence than with prior numerical tolerancing methods. The methodology used in CMC for color tolerances heavily relied on visual evaluations to establish the nonlinear relationships between L, c and h. If a sample falls outside the CMC limits, CIELab Lch data may be helpful when used to address the correction problem.

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