When a dog has two different colored eyes, it's called heterochromia. While it can occur in humans, it's much more common in dogs, cats and horses. The distribution of melanin in the iris determines eye color. More melanin means a darker eye, like brown. Less melanin results in green or blue eyes. Heterochromia can also cause one eye to lack melanin altogether. Australian sheepdogs, Siberian huskies, American foxhounds, Alaskan malamutes and shih tzus are all more likely to have one blue…