if you get a lot of blood inside the eye that can

It is, however, possible for injury to alter iris colour, says Mackey. "That can happen – if you get a lot of blood inside the eye that can stain parts of the eye. Or you can just have all the pigment scrambled everywhere and it settles."More commonly, infection is the root cause. A famous case of true heterochromia, where the colour of the irises differs, is the actress Mila Kunis, whose right eye is brown and left green. Kunis' heterochromia resulted from an infection of the iris, which destroyed some of the pigment in her left eye.