Thanks Chiilaa you explained a lot for me. I don't know much about colours other then the basics so I wasn't sure about the grey-chestnut without a picture. I love my boys colour even though I'm not a big fan of chestnuts. I had figured he was chestnut and you can only see the white hairs if you're standing close to him.
Yep, depending on where you are and what discipline you ride usually dictates what term you use. I always used 'sorrel' to describe your typical red horse that ranges from orangey to bright red, then I would use chestnut to describe a horse that was the color of blood or darker.
Either way, white hairs means that he has some gene that is causing roaning.
No, a full body picture would be more ideal. I'll go look in your barn.
ETA: I looked. He's just a chestnut. A lot of chestnuts have random white hairs mixed in. If I remember correctly, the roan gene does not exist in Thoroughbreds. Rabicano does, but he doesn't have enough for me to want to call him that. I think tinyliny mentioned in another thread that sabino causes the white chin. Sabino also causes some "roaning", it so that could be causing his white hairs.