The third man would have no idea what color he is and would not be able to answer because you hinted that he would have known his color(red) if the first two men where blue. So he could be red or blue.
That means that the two men in front could not be blue/blue. They could either be a blue and a red or a red and a red. Assuming the men are very smart, they would catch on to this.
According to the combinations above(a blue and a red or a red and a red). If the first man is blue, then the second guy would know he is red. so he would be able to answer. If the first man was red, then the second guy would have to stay quiet because he could not know his color. He could be a blue or a red.
Again, according to combination (a blue and a red or a red and a red) If the first guy is as smart as the other guys, he would realize, that if his hat was blue, the second guy would have answered red . Since the second guy didn't answer. He knows the only color his hat could be is red and he would be able to answer.
Basically, there could be two answers. the first guy could answer red in one solution or the second guy could answer red in the other solution.
I Hope this makes sense to you.