Paul McCartney dyes his hair. The 70 year old admitted that he dyes his hair. The reason why people call his sir Paul is because he was appointed by the Queen as a knight then given that title. You can read more about him at http://en.wikipedia.org/wiki/Paul_McCartney.
I think he does dye his hair. I think he's around his 70s or close to it. Anyway he was appointed by the Queen as a knight and given the title since she enjoys his music so much. Same goes for Elton John