I would guess that she was born brown, but is now greying out. She will eventually be either flea bitten, or "white", she may retain some dark points, my Arab did that. She's still got a pretty black mane, and a half black half white tail, and she's 8 now, her hocks and knees are also still pretty dark. I think grey horses are neat because their coat changes from season to season, so you never quite know what they are going to look like.
Definately gray! Often one of the first signs of a horse going gray is that the bottom of their tail will get very washed out - much lighter than it would if they were going to stay dark. You can see that clearly in your horse in the third photo.