As I have mentioned, having variations in the horse colors for this project is very difficult.
The primary constraint is that nearly every horse must be some shade of dark brown.
I have tried to achieve the separation by making some a bit more red, while others, such as this one, were darker with cooler shadow areas. This meant mixing more blue with brown in those sections.
On other horses, I even added a tiny bit of yellow to the brown... once again in an effort to make things somewhat different. Of course, there were also other markings, such as some 'socks', as I did here.
The white patch on the face is also a fun change here and there!
This puts that theory on display. Reddish on the left, more yellow next, then white, then the darkest colored horse on the right, with a few markings.