No just like a pinto is not a racehorse.Palomino is a color not a breed though some Quarter horses can be Palomino racehorses. As can Thoroughbreds.
Large races like the Kentucky Derby allows 20 horses. The average number for smaller races is 8 to 10 horses.
race
Racehorses begin racing at the age of 2 and can race upto the age of 12 -13 , most retire at the age of 10 or earlier through injury.
if the horse keeps losing races it will be retired