The gene which makes a cat pure white is dominant. This allele inhibits the normal function of the coloring cells, so that no color is produced. A completely white cat thus carries the genes for red/black, agouti/non-agouti, dilution/non-dilution, etc. The gene for white is thus epistatic.
Pure white cats often have a color spot on the head when they are born. It disappears when the cat has developed its adult fur. This spot can reveal what color the cat has underneath the white.
White cats can have yellow eyes, blue eyes or one blue and one yellow eye (odd-eyed). One doesn't know how the eye color in this case is inherited.
White cats are often deaf. This is due to a degenerative change of the cochlea in the inner ear. It is definitely more common with deafness in blue-eyed white cats than in yellow-eyed, but there are yellow-eyed white cats that are deaf and blue-eyed cats with normal hearing. Cats can also be deaf on only one ear. Odd-eyed cats are often deaf on the ear which is situated on the same side as the blue eye.
Denominations: W = white w = non-white