Thabit said that Anas was asked about the hair-dye of the Prophet ﷺ. He replied:
He did not dye his hair, but Abu Bakr and 'Umar dyed their hair.

حَدَّثَنَا مُحَمَّدُ بْنُ عُبَيْدٍ، حَدَّثَنَا حَمَّادٌ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ، أَنَّهُ سُئِلَ عَنْ خِضَابِ النَّبِيِّ، ﷺ فَذَكَرَ أَنَّهُ لَمْ يَخْضِبْ وَلَكِنْ قَدْ خَضَبَ أَبُو بَكْرٍ وَعُمَرُ رَضِيَ اللَّهُ عَنْهُمَا .