Odd-eyed cats have a striking condition called "heterochromia iridis" which means irises that are different colors. They typically have one blue eye, and the other is either green, brown, or yellow.
An odd-eyed cat is a cat with one blue eye and one eye either green, yellow, or brown. This is a feline form of complete heterochromia, a condition that occurs in some other animals, including humans. There is also partial heterochromia, where there can be one blue eye and one eye that is partially blue and partially another color. The condition most commonly affects white-colored cats but may be found in a cat of any color, provided that it possesses the white spotting gene.
The odd-eyed coloring is caused when either the epistatic (dominant) white gene (which masks any other color genes and turns a cat completely white) or the white spotting gene (which is the gene responsible for bicolor and tuxedo cats) prevents melanin (pigment) granules from reaching one eye during development, resulting in a cat with one blue eye and one green, yellow, or brown eye. The condition only rarely occurs in cats that lack both the dominant white and the white spotting gene.
Odd-eyed cats are popular within several breeds, including, Van cat, Turkish Van, Turkish Angora, Sphynx, Persian, Oriental Shorthair, Japanese Bobtail and Khao Manee. In Turkey, Ankara Zoo has a breeding program to preserve pure white Turkish Angora cats with blue and amber eyes. The zoo specifically prized the odd-eyed Angoras who had one blue eye and one amber eye, as the Turkish folklore suggests that "the eyes must be as green as the lake and as blue as the sky." The mascot of the 2010 FIBA World Championship, hosted by Turkey, was an anthropomorphized odd-eyed Van Cat named "Bascat".