I have a 50/50 paint, but his legs are all white. They tend to be the most discolored...he has a slough in his field and he seems to enjoy running through it at full speed. He rolls some, but I think he's a pretty clean horse. He does go out in a fly sheet with a neck thing, and during the fall, winter and spring he goes out in a turnout blanket, winter time with a neck thing.
His biggest issue is that his white legs (pink skin underneath) are susceptible to scratches, and he gets hosed off everyday when he comes in. Every spring he gets a bad case, even if I'm diligent and try to head it off.
I buy Mane and Tail shampoo and conditioner at Walgreens, KMart, etc, when it's on sale (like $3/bottle for big bottles), and save the Quik Silver for his legs a couple times a year.