It was narrated from Anas that:

The Messenger of Allah [ﷺ] 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.

أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ حَدَّثَنَا عَبْدُ الصَّمَدِ، قَالَ حَدَّثَنَا الْمُثَنَّى، - يَعْنِي ابْنَ سَعِيدٍ - قَالَ حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم لَمْ يَكُنْ يَخْضِبُ إِنَّمَا كَانَ الشَّمَطُ عِنْدَ الْعَنْفَقَةِ يَسِيرًا وَفِي الصُّدْغَيْنِ يَسِيرًا وَفِي الرَّأْسِ يَسِيرًا ‏.‏