Color Color Color (American English), or colour (Commonwealth English), is the characteristic of human visual perception described through color "categories", with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them. This reflection is governed by the object's physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically
Color difference Commonly used values are 2:1 for acceptability and 1:1 for the threshold of imperceptibility. The distance of a color formula_27 to a reference formula_28 is: CMC l:c is designed to be used with D65 and the CIE Supplementary Observer. The formula is not a metric but rather a quasimetric because it violates symmetry, parameter T is based on the hue of the formula_32 alone. This reference color means that the color difference from the first color to the second color is different than the color distance from the second color is to the first. Tolerancing concerns the question "What is