My fav. subject, and in my fav. color! You've handled the subtle variations of light very well! I haven't seen much of your work, but if this isn't your normal style, then I would say explore this losser style further as it obviously suits you!
Definately has the Mustang "wildness" to it, love the mane!
You don't mention, but I assume this is acrylic?
Well done and look forward to more!