It looks like a red-point Birman to me, possibly a chocolate or chocolate lynx, perfectly acceptable under at least one of the big cat associations like CFA or TICA, can't remember which ones. Whatever it is, its legit.
Birmans come in lots of colors, not just white and grey, and I wonder where you even heard that, since there is no official "grey" coloration in Birmans. My Chay, for instance, is chocolate, which is a brown-type color. Blue (very dark grey), lilac (a sort of pinkish grey/purple color), chocolate (dark brown around the nose), and seal (darker brown across most of the points) points are allowed in all cat associations, and many if not all also include the red , cream points, and lynx cats. Hope that helps! Let me know if I can provide any other information!