Many industries that use coloring processes have to supply products that have the same color and apperance (gloss, texture, etc.). Deviations from the originalcolor, the standard, have to be as slight as possible. In practice it may not be possible to match the standard perfectly. Even within the same sample (e.g. a T-shirt), we may see some color differences. We need a way to numerically describe the color difference.

Numericalcolor differences can be caculated from instrumental measurements of the standard and the trial. the distance between the two sets of color coordinates in a given three-dimensional color space represents the color difference. Instrumental measurements can determine differences between a standard and a trial that are not visible to the human eye so that a 0.00 color difference is an unrealistic goal.

DE = ((DL)² + (Da)² + (Db)²)^1/2    or    DE = ((DL)² + (DC)² + (DH)²)^1/2

The CIELAB color space id often used in the calculation od color differences. DE* represents the total color differene, which is made up of the differences in chroma (DC* - more brilliant/duller), hue (DH* - greener, yellower, bluer, redder) and lightness (L* - lighter or darker). The total color difference can also be made up the difference in lightness (DL*), in the red-green coordinate a* (Da*) and in the yellow-blue coordinate b* (Db*).