Eye Color - Classification of Color

Classification of Color

Iris color can provide a large amount of information about a person, and a classification of various colors may be useful in documenting pathological changes or determining how a person may respond to various ocular pharmaceuticals. Various classification systems have ranged from a basic light or dark description to detailed gradings employing photographic standards for comparison. Others have attempted to set objective standards of color comparison.

As the perception of color depends on viewing conditions (e.g., the amount and kind of illumination, as well as the hue of the surrounding environment), so does the perception of eye color.

Eye colors range from the darkest shades of brown to the lightest tints of blue. To meet the need for standardized classification, at once simple yet detailed enough for research purposes, Seddon et al. developed a graded system based on the predominant iris color and the amount of brown or yellow pigment present. There are three pigment colors that determine, depending on their proportion, the outward appearance of the iris: brown, yellow, and blue. Green irides, for example, have blue and some yellow. Brown irides contain mostly brown. Eye color in animals other than Homo sapiens is differently regulated. For example, instead of blue as in humans, autosomal recessive eye color in the skink species Corucia zebrata is black, and the autosomal dominant color is yellow-green.