This is (was) a wonderful discussion. Besides the Leliepvre watercolors, what has helped me are two works: the Andrea Press book on ‘Painting Horses’, it is pretty basic but a good intro; and most of all, ‘Color Formulas & Techniques for the model horse artist’ by Carol Williams. In my opinion, it is the Bible on horse painting. Besides the dozens of paint formulas for oils for the MANY different types of horse color types, it explains everything about horse anatomy that would be of interest for the painter. It is out of print but can occasionally be found on eBay where I found my very used copy. It is a 3 ring binder 9” x 7” with the paint formula cards separate from the binder. I cannot recommend this work enough when I look a color reference photo of the horse I want to paint, I then say to myself, OK, now how do I accomplish that? This work clearly answers that perplexing question.