from APHA
[edit] Paint or Pinto?
A Pinto differs from a Paint solely by bloodlines. A Pinto may be of any breed or combination of breeds, though some Pinto registries may have additional restrictions. (Some do not register draft horses or mules, for example.) For a horse to be registered as an American Paint Horse however, it must have registered American Quarter Horse, American Paint Horse, or Thoroughbred parents. Therefore, all Paint horses (except for the small number of "solids" allowed into the Paint registry) could be registered as Pintos, but not all Pintos qualify to be registered as Paints.
[edit] History
The American Paint Horse shares a common ancestry with the American Quarter Horse and the Thoroughbred. A registered Paint horse should conform to the same "stock horse" body type desired in Quarter Horses: a muscular animal that is heavy but not too tall, with a low center of gravity for maneuverability, and powerful hindquarters suitable for rapid acceleration and sprinting.
When the American Quarter Horse Association emerged in 1940 to preserve horses of the "stock" type, it excluded those with pinto coat patterns and "crop out" horses, those born with white body spots or white above the knees and hocks. Undeterred, fans of colorful stock horses formed a variety of organizations to preserve and promote Paint horses. In 1965 some of these groups merged to form the American Paint Horse Association.