Colorful silks adorn jockey Jean CruguetBy Ashley Herriman

Silks or colors, worn by each jockey in a race to represent a horse’s owner, are among the oldest traditions in racing. 
Colors initially evolved out of necessity – in ancient Rome, chariot drivers wore different colors so spectators could differentiate between them during races.
For much the same reason, 19 members of the English Jockey Club registered their colors at Newmarket in 1762 “for the greater convenience of distinguishing the horses in running.” Four years later, the Philadelphia Jockey Club followed suit and silks have remained in widespread use ever since, though their original purpose to differentiate horses has been rendered mostly obsolete with the addition of numbered saddle clothes corresponding to post position and program number and the public address system.
As racing has changed, so too have colors.  Called silks because the early variations were, in fact, silk, today most are actually nylon or lycra. Aerodynamic silks have become more popular in recent years. 
While in their earliest iterations silks were merely different colors, today the designs can be quite intricate, ranging from geometric patterns to pictures and symbols. 
Approximately 28,000 sets of silks are registered with The Jockey Club. In New York State, owners must register their stable names and silks with The Jockey Club in order to start a horse at any of the four Thoroughbred tracks in the state. (The three NYRA tracks, Aqueduct Racetrack, Belmont Park, and Saratoga Race Course, as well as Finger Lakes Race Track, which is not affiliated with NYRA.) 
Per The Jockey Club rules: “By registering stable names and silks with The Jockey Club, an owner is guaranteed exclusive use of the stable name and silks design when racing Thoroughbreds in New York State. However, owners who race horses in other states are welcome to, and often do, register their stable name and silks with The Jockey Club as well.”