The melanin in newborns is concentrated in the folds of the iris. When a baby is a few months old, the melanin moves to the surface of the iris and gives the baby his or her permanent eye color.

Variations in eye color range from light blue to dark brown and are inherited. Eye color is chiefly determined by the amount and distribution of melanin within the irises. If melanin is present only in the epithelial cells that cover the posterior surface of the iris, the iris appears blue. When this condition exists together with denser than usual tissue within the body of the iris, it looks gray. When melanin is present within the body of the iris, as well as the epithelial covering, the iris appears brown. Green and hazel eyes result from an increase in the amount of a combination of yellow and black melanin.