http://www.azcentral.com/arizonarepublic/local/articles/0501clay0501.html

"Has a white horse ever won the Kentucky Derby?

I'm sorry, but I don't know. I do not follow the sport of kings closely.

However, the Derby is a race for Thoroughbreds and they tend to be
kind of brown or roan-ish. Or sometimes grayish.

There are white Thoroughbreds, and this has something to do with the
dominant heterozygous solitary gene, and if you think I am going to
explain that to you for what I get paid, you are mistaken. But as far
as I can tell, none of these white ones has ever won the Derby. If
you know otherwise, speak up."

Of course we know that no white horse has won the Kentucky Derby &
that (acknowledged) white Thoroughbreds are rare and have just
recently been recognized by the Jockey Club. Anyone want to send him
a well-written/researched response on it?