Ten Hats in a Line

10 players stand in a line. Each wears a red or blue hat, assigned independently by a fair coin. Each player sees all hats in FRONT of them but not their own nor those behind. Starting from the back of the line, each player in turn announces a single guess of their own hat color, heard by everyone. They agree on a strategy beforehand (no communication after hats are placed except the public guesses). Using the optimal parity strategy, how many of the 10 players are GUARANTEED to guess correctly regardless of the hat assignment?