The Irish blind man mystery

In the year 1341, in Scotland, northwest of Edinburgh, past Bannockburn along the bridge of Allen Road, and the end of the Firth of Forth is Stirling Castle, which has a small keep (jail).

One fine day the Sheriff of Cambus delivered a bad actor to the Turnkey (jailer) of the Stirling Castle keep.

The turnkey had a problem since the keep was full to capacity. The turnkey would need to free a prisoner or chop off a head to make room for the new prisoner.

After a few hours the turnkey devised a plan to make room. He had three prisoners in the keep who were disabled. The release of one of them would not cause a big problem for the king. One prisoner had a peg-leg. One had a missing arm. One was blind.

The turnkey placed the candidates in high backed chairs in his office, so that each faced the other in a triangle. The two that could see were blindfolded and a guard was placed in back of each, so the candidate could not see his own guard.

The keep had five guards and all of them had red hair, as many other Scottish men of the lowlands. But three of the guards red hair had turned white. This was well known to the prisoners.

The peg-leg man had his blindfold removed and was told that he could try to guess the hair color of the guard in back of him by looking at the hair color of the other two guards. If he was to guess and was in error he would be killed. If he made a guess and was correct he would be free. The peg-leg man declined to make a guess.

The one-armed man had his blindfold removed and he also declined to make a guess.

The turnkey was not pleased with the results of his game until the blind man stated that he knew the color of the hair of the guard in back of his chair, and as a result the blind prisoner gained his freedom.

Your problem is as follows: 1. How did the blind man know? And, 2. What was the color of the hair of the blind man’s guard?

Are you as wise as the Irish blind man?