Definition of "pinto"

Chick Norris leaned low over his pinto.

1936 August, Joseph S. Fleming, “Flying Hoofs. Chick Norris again leads his Mounted Patrol”, in Boys' Life, page 10

While Profane, dreamy, went on to tell of his nights with the Alligator Patrol, and how he’d hunted one pinto beast through Fairing’s Parish; cornered and killed it in a chamber lit by some frightening radiance.

1963, Thomas Pynchon, V.