The Chinese, Persians, and Greeks as well, became horsemen of note. Accounts of Spotted color horses, are recorded in the histories of these people. Many spotted horses were chosen mounts of emperors, kings, and royalty. The Chinese, with a heritage of recording history in art, depict many horses in paintings that show clear spotted coat patterns similar to the American Appaloosa. Historians believe that reference to the "blood sweating" white horse in China was actually reference to the "leopard" coat pattern.
Spotted horses were common in China for at least the last thirteen hundred years, but they never composed more than a small fraction of the horses of the country. There is no accurate estimate of the ratio of spotted horses to others, but it seems improbable that this could have been greater than one in ten, even in selected stock. Gradually the Chinese allowed their horses to deteriorate. European visitors in the 19th century found the average horse more like those of long ago - small, coarse, and poorly kept. Paintings of this period still show some good stock, with a spotted horse here and there, and spotted horses were raced at Shanghai as late as 1931.
In Persia evidence indicating the presence of spotted horses in both earlier and more abundant. The Persian plateau passed from one conqueror to another until the Moslems came from the South in 640 AD. Of course there are gaps in the records of Persian art, but extant art objects produced from the 6th century AD to the present show spotted horses. Here again is an indication that such horses were common in Persia long before this time.
source: Jan Davis The Complete Appaloosa Horse p 14
Francis Haines Appaloosa the Spotted Horse in History p 25-37