These colors are perfect. Nice shadows of body and neck not invading his face. Composition is great,although I wish he was looking at me, regardless, this is a quite the equestrian study. Good luck.-8-
He/she looks like he/she is posing for you. I think the sky is a bit bright for the rest of the shot. Perhaps burning it a little? I like where you have positioned the horse in the frame and your focus is good.
You've got such great form in the horse's body that I think losing much of the sky would have been a better choice. Also not sure the cyan and brown complement each other....a case for sensitive use of selective desaturation???