I guess it depends on your definition of a white horse, I consider a horse that is completely white (pink skin, white fur) to be white, no matter what his genetics say (he could easily be genetically a grulla, but if there is no color (or very, very little), what difference does that make?), genetics would only matter if I was going to breed the horse. Now to be clear I do not think genetics are unimportant, but to me it's like a sorrel/chestnut w/ agouti, or a black w/ cream, a bay w/ red, etc. if I can't see it or don't plan to breed the horse, knowing this doesn't change the fact that the horse is sorrel/chestnut, black, or bay. A gray horse is gray, he may have started out bay/grulla/buckskin/dun/black/ or purple with green polka dots, in the end he's just gray. I feel the same about a white horse.
My neighbor had a white horse with brown eyes, she had a foal that was white w/ blue eyes, no idea what their genetics would say they were, I never saw any color at all on them. To me they were both just white.
So maybe there are no such thing as white horses, but there are horses that are white!
That said cremello is not white, cremello is cremello! I couldn't find the pics of Brisco, but I'm currious what's so bad about him being cremello? Knowing the color of his parents would be very helpful, but I'm guessing you don't know what color they are? Since the question has been asked atleast a few times and you haven't bothered to answer? My cremello looks VERY white! I can't destinguish any white markings because he's so white looking, but I've only owned him through winter, we'll see if his color darkens any when he sheds out for summer. But he is a cremello!
Of course I'm guilty as anyone when it comes to curriousity, if I was in a similar situation as Amberly, w/a horse others swore was one color and I was convienced was another, that could be easily proven w/ a test (and I had the cash) I think I'd have to have it done, just to either prove to myself and others that I was right, or to find out once and for all if I was wrong. I've had passing curriousities about my colt (destined to be a gelding), I know what color he is, but I wonder if he's homozygous for dun? Or black? I know my mare's color genetics, and there are times I'll see another horse that I really like, or is an attractive color (mare's or geldings generally), and I think, if I bred that horse to my mare the baby would be x_____ or x_______ or whatever, it's just fun!
Just my take on it.