Heterochromia

Heterochromia is a variation in an animal's coloration, most often a difference in the colors of the left and the right eyes' irises, but also a variation in the color of hair or skin. Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment). It may be inherited or caused by genetic mosaicism, chimerism, disease, or injury. It occurs in humans and certain breeds of domesticated animals.