Yes, Gold is smart. He knows that since he killed Kovu after he became Kiara's mate, they probably already had a cub. Gold mated with Kiara first, though, before Kovu and Kiara became "mates", so he knew the cub was still inside of her when he killed Kovu. Therefor, since Kovu is brown and one of Kiara's newborns is brown, Gold had enough common sense to put two and two together
