After assembling the horses, I primed them all with a primer grey. Then I divided them into 3 groups. One set was spray painted with red brown. These would be painted as duns, light bays, chestnuts and maybe some piebalds. Another set was spray-painted black. These would be painted as blacks and dark bays. Finally, the last set was spray painted with a lighter grey. They'll be painted as greys and a few roans. As an illustrator for my day job, I managed to amass quite a bit of horse reference material and painting model horses accurately has become quite an obsession with me. Here are some older model horses I've painted. I hope my Rohan horses end up much better. Here's the wiki entry on Equine Color.