The Stark Raving Mad King

A stark staring mad king told his 100 wisest men he was about to line them up and that he would put either a red or a blue hat on their heads. Once lined up, they would be allowed neither to talk to each other nor to look behind or put off their hats.

The wise men would be allowed to see just all hats in front of them, and certainly not their own hats. They would also be allowed to hear the answers from all wise men behind.

Then the King would come up to the last in a row and ask the only question, "What color is your hat?" The wise man would only be allowed to answer "red" or "blue" and nothing else. If the answer was incorrect then the wise man would be silently killed. If the answer was correct then the wise man would stay alive but had to remain absolutely silent.

The king would then move on to the next wise man and repeat the question.

The king made it clear that if anyone broke the rule then all the wise men would die. However he allowed them to consult with each other before lining them up. The king listened to all they were talking about to be sure they are not going to cheat. Any odd movement, any cough would mean they broke the rule.

So what is the highest number of wise men who could certainly stay alive?