If the batter hits the ball and the ball hits you and then the plate then goes in to fair territory is it a fair or foul ball?

Once again the answer to this lies in the definition of a foul ball listed in Rule 2 of the MLB rule book. A FOUL BALL is a batted ball that settles on foul territory between home and first base, or between home and third base, or that bounds past first or third base on or over foul territory, or that first falls on foul territory beyond first or third base, or that, while on or over foul territory, touches the person of an umpire or player, or any object foreign to the natural ground. This answer depends entirely on the position of the "you" in this question. The batter, the umpire and the catcher are all generally in foul territory at the time the batter swings. If the batted ball hits any one of those people while they are in foul territory, the ball is immediately foul. However, if in the umpire's judgement, the contact was made while over or on fair territory, the ball is fair. Nothing that occurs to the ball after the contact will change whether it is fair or foul.