It's on the horse texture ... although exactly where I can't tell you. I know it's default "black" with the original textures (might be purple, I didn't look too closely at it), but I was toying with my California Chrome skin and it was white on that. Only file I've played with are the horse textures so I know it's on that. Screwy thing is, only white areas I have on the texture are the leg wraps and the trim on the saddle blanket which I forgot to turn off. >_> It can't share a texture with the blanket because if it did, it would be gold with the default horses and white with my California Chrome. It's not tied to the bridle texture, either, since I had California Chrome with a black bridle at the time. I'll probably narrow down the exact spot through trial and error eventually or someone else will beat me to it. My California Chrome is nearly done. Currently toying with his hood/visor (and no, it won't have DAP on it due to the mirroring the texture does). Then I have a whopping 53 other horses I intend to do.
Although some are similar so I won't have that many to do. Going to start weeding out horses shortly and figure out the group I really want to do.** Edit **
Tried to find the nose band and I'm at a loss. I did a rainbow horse texture which helps me narrow down locations, and the noseband popped up white when I had no white on the texture. Did another pure black texture, and (here's the kicker) the noseband was white for one horse and black for another one despite both having the pure black texture.
So I'm at a loss. Could be on the jockey texture which is the only other spot I can think of. I found the blinker location on the horse texture and the visor is also on the horse texture so why not the noseband? No reason for it to have its own file. The visor's more deserving of its own file than the noseband, but the visor is on the horse texture. It's really bizarre. Makes me wonder if it's a bug and should be on the horse texture but is attached to something else instead. Happens from time to time.