Sunan an-Nasa'i Book 48, Hadith 47
That he asked Anas: "Did the Messenger of Allah dye his hair? He said: "His gray hair didn't go far, it was only a little at his temples."
"I saw Ibn 'Umar dyeing his beard yellow with Khaluq and I said: 'O Abu 'Abdur-Rahman, are you dyeing your beard yellow with Khaluq?' He said: 'I saw the Messenger of Allah dyeing his beard yellow with it, and there was no other kind of dye that was dearer to him than this. He used to dye all of his clothes with it, even his 'Imamah (turban).'"
The Messenger of Allah did not dye his hair; his gray hair were only a little beneath his lower lip and at his temples, and a little on his head.