Eye color for a plausible argument stating that some eyes can or do change, based on chemical reactions and hormonal changes within the body. Studies on Caucasian twins, both fraternal and identical, have shown that eye color over time can be subject to change, and major demelanization of the iris may also be genetically determined. Most eye-color changes have been observed or reported in the Caucasian population with hazel and amber eyes. Carleton Coon created a chart by the original Martin scale. The numbering is reversed on the scale below in the (later) Martin–Schultz scale, which is (still) used in physical anthropology.
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