Hat

Of three prisoners in a certain jail, one had normal vision, the second had only one eye, and the third was totally blind. The jailer told the prisoners that, from three white hats and two red hats, he would select three and put them on the prisoners' heads. None could see what color hat he wore. The jailer offered freedom to the prisoner with normal vision if he could tell what color hat he wore. To prevent a lucky guess, the jailer threatened execution for any incorrect answer. The first prisoner could not tell what color hat he wore. Next, the jailer made the same offer to the one-eyed prisoner. The second prisoner could not tell what color hat he wore either. The jailer did not bother making the offer to the blind prisoner, but he agreed to extend the same terms to that prisoner when he made the request. The blind person said: "I do not need to have my sight; From what my friends with eyes have said, I clearly see my hat is________!"

How did he know?