Interestingly, white cats have traditionally been the bringers of bad luck, not black. In the UK, black cats are usually seen as lucky, and in Ireland, black and white cats are both considered lucky, but a cat with both black and white spots are unlucky.
White animals used to be culled because they were more susceptible to genetic problems, including cancer, deafness, and blindness. That, and if they were bred for hunting, they would be more visible to the prey. That is why white animals were originally unlucky. Somewhere along the road, when the myths traveled to america, black animals were charged as being unlucky instead.