One of the reasons movie horses were chosen was for their color, and ease it matching it.

Color was a consideration when choosing a movie horse because of the need for "stunt doubles" or stand ins as Dianne pointed out. A number of them were white or black notably the Lone Rangers Silver, Hopalong Cassidy's Topper, Zorro's Tornado and Lash LaRue's Black Diamond. The Cisco Kid's Diablo was almost impossible to find a double as he was an Overo paint, and you can pick out Diablo's doubles a mile away. Palomino or Chestnut like Roy Rogers Trigger and Gene Autrys Champion were not hard to double up, but also not real easy. There are two sure fired way's to identify "The" Trigger, and "The" Trigger Jr. One is the blaze on their face, and the other is what made them distinctive. If you know the other, tell me which one this is?