Here ya go:
BTW, there are some details relevant and I'll toss 'em in.
They are all in earshot of one another. They can all see each other's hats but not their own, except the blind guy of course.
The warden asks the first guy, he says, "I don't know". Both the other two guys hear this. The warden asks the second guy. He knows the first guy saw either a white/white, red/white, or white/red but not red/red. He looks at the blind guy and does not see red. If this guy (second guy) had seen red on the blidn guys head he would have known that his own had to be white. Therefore, since the second guy did not know what color his own hat was the blind guys cannot be red. The blind guy heard both say they didn't know and reasoned this for himself and concluded that his own could not be red therefore it must be white.