My dad races trotters.... He has his own colors registered and every horse he sends out uses these colors.. This would suggest to me that a horse will wear its owners colors, so I would imagine that it will always wear the same (unless it gets sold...)

I can't help you more than that but, I would suggest that there would be a list somewhere of colors and who they are registered to. I would imagine though, that it would be very hard to give an accurate description of the colors with enough certainty to track the owners down if you only get a glimpse of the race...