Eye Colour

The genetic switch is located in the gene adjacent to OCA2 and rather than completely turning off the gene, the switch limits its action, which reduces the production of melanin in the iris. In effect, the turned-down switch diluted brown eyes to blue. If the OCA2 gene had been completely shut down, our hair, eyes and skin would be melanin-less, a condition known as albinism.

The colour of the iris is determined by the amount of pigment in the iris structure. No pigments at all will result in a pink iris, in the case of an albino. Some pigments cause the iris to appear blue Whereas increasing the amount of iris pigments produce green, hazel, and brown irises.
Rarely, one iris can be a different color than the other iris. This is known as “heterochromia irides” and is determined genetically. Also, a section of one iris may be a different color from the rest of that iris; this is known as “heterochromia iridum” or “sectoral heterochromia iridis.” Usually, if on e of these conditions is present, it is noticeable at birth.

Unlike what commonly is believed, the iris does not change colors in an adult . Iris color may appear to change, depending upon the color of clothing a person is wearing on a particular day. However, this color change does not actually take place; it is a misperception by the observer, often due to variations in lighting.