Yes, there is a colour called dominant white, as mentioned before. However, the origins of this is gene and its inheritance are still being studied. Dominant white horses are born entirely white, with pink skin. The occurrence of this gene is extremely rare. Many horses thought to be dominant white are proven to have other explanations for their white coats. Some pintos with multiple pinto patterns, have patterns that "cover up" any colour they would have had, making them appear white with pink skin. Sabino (a type of pinto pattern), when expressed fully, can create the illusion of an entirely white horse. Sabino is found in the thoroughbred population, so many of the "white" thoroughbreds in the google search provided by the previous answerer could be sabino white instead of dominant white. Sabino is bred into non-pinto breeds because in moderate or minimal expression, a horse will express white below the knees and hocks and have white face markings and a chin spot. The horses are thought not to be pinto, so they are bred into the non-pinto breed and occasionally markings above the knees and hocks and sabino whites will pop up in future generations. Cremello horses often appear white. They have pale skin and their fur is a very pale cream colour that can sometimes look white. And of course, grey horses often turn completely white as they age, though their skin is usually dark. True albino horses have never been documented to exist. Some appaloosas can look white as well. Some few spot appaloosas have very minimal colour expression. My dad's leopard appaloosa mare is losing her spots as she ages. She is turning white, but she is non-grey.