I know there is an answer that explains where the person is, and how to figure it out on your own, but it only Applies to Black and White and some previous games. Is there a person who tells me the type of a hidden ability in X and Y? If so, where is he?
In X/Y, the NPC who will tell you the type a given Pokémon's Hidden Power is located in Anistar City, in the house next to the boutique. He is also the NPC who gives you TM10 (Hidden Power) in the first place.