I found this which might interest others
Domestication led to horse color explosion - Technology & science - Science - DiscoveryNews.com | NBC News
"The study's pinpointed date for the first major domestication of horses supports yet another research team's findings. Alan Outram of the University of Exeter and colleagues recently studied ancient horse bones, and came to three conclusions.
The first was that horse domestication dates back to the Botai Culture of Kazakhstan circa 5,500 years ago. The second is that "bit damage," caused by harnessing or bridling, reveals these early, domesticated animals were ridden. Finally, traces of horse milk fat on ancient pottery shows the Kazakhstan horse riders were consuming an alcoholic drink called "koumiss" made out of horse milk.
Outram said, "The domestication of horses is known to have had immense social and economic significance, advancing communications, transport, food production and warfare."
Leaders such as Alexander the Great, Genghis Khan and Francis Pizarro later forever changed the world's political landscape by conquering vast tracts of land with mounted warriors astride often colorful horses.
© 2012 Discovery Channel
Going way back to the FIRST evidence of mankinds use of horses would be a wondrous thing to study I think but already I notice that man was instrumental in developing different coat colors because he simply LIKED a horse of a flashier color. The earliest " horse breeders" made their selections for various reasons..... one of them would be a docile nature. You don't breed horses that are trying to kill ya.
Then you decide what traits are more useful to you.... Big and strong?.... thinner and faster?.... all have reasons to be developed by early man........ but coat color was a personal choice I think. Earliest horses would have been very drab. They naturally would have blended into their surroundings. But when they interacted with humans something strange began to happen.... and I think the humans had alot to do with the change.
Flashier coat colors began appearing. Speaking from years of breeding horses myself I can vouch for the fact that the flashier colors usually damand a higher price. In the ancient world white horses were held out for the leaders..... as well as pure blacks. I believe that Alexander the Great prized his pure black horse highly....Its a fascinating study....
But the idea that horses and mankind crossed paths so much earlier than expected? THATS something thats going to be fun to think about. Linda