Here I go! Im pretty sure these colors are legal, there may be more but I think these are the main ones:
Arabian - gray, chestnut, bay, roan, solid black, Sabino, Rabican, Dominant White,
Pinto (color registry) - (all with white spots, but these are the main color) Black, Brown, Bay, Bay Road, Blue Roan, Buckskin, Gray, Grullo, Dun, Perlino, Cremello,Chestnut, Red Roan, Palomine, Red Dun, Sorrel
Quarter Horse - all solid colors
Clydesdale: bay and brown, some gray and black, markings on legs, face, sometimes on the body are frequent.
Percheron - gray, occasional black or bay without white markings
Throughbred - bay, dark bay/brown, black, gray/roan, chestnut, rarely white, palamino and cremello very rare
Appaloosa - six patterns (white blanket, spotted blanket, leopard, snowflake, frost/frosted tips, and marble)with any color, molted skin around eyes, lips, and genitalia, striped hooves, and white sclerea around the eyes.
Andalusian - mostly gray (all variations), bay, black, chestnut, grulla, palomino, and Isabella, lineback dun and leopard Appaloosa extremely rare. Spanish registry only accepts grays, blacks, and bays. The Portugese Stud Book allows horses of any color. White markings are not desireable.
Hanoverian - any solid color, commonly bay, brown, black or gray
Oh, the color isabella or isabelline, is like pale grey-yellow, pale fawn, pale cream-brown or a parchment color...