I asked Anas, "Did the Prophet ﷺ dye his hair?" Anas replied, "The Prophet ﷺ did not have except a few grey hairs."  

سَأَلْتُ أَنَسًا أَخَضَبَ النَّبِيُّ ﷺ قَالَ لَمْ يَبْلُغِ الشَّيْبَ إِلاَّ قَلِيلاً  

Anas was asked whether the Prophet ﷺ used a a hair dye or not. He replied, "The Prophet ﷺ did not have enough grey hair to dye, (such that) if I wanted to count the fading hairs in his beard (I could have)."  

عَنْ خِضَابِ النَّبِيِّ ﷺ فَقَالَ إِنَّهُ لَمْ يَبْلُغْ مَا يَخْضِبُ لَوْ شِئْتُ أَنْ أَعُدَّ شَمَطَاتِهِ فِي لِحْيَتِهِ  

ʿUthman bin ʿAbdullah bin Mauhab said, "My people sent me with a bowl of water to Um Salama." Isra'il approximated three fingers ('indicating the small size of the container in which there was some hair of the Prophet. ʿUthman added, "If any person suffered from evil eye or some other disease, he would send a vessel (containing water) to Um Salama. I looked into the container (that held the hair of the Prophet) and saw a few red hairs in it,"  

أَرْسَلَنِي أَهْلِي إِلَى أُمِّ سَلَمَةَ بِقَدَحٍ مِنْ مَاءٍ وَقَبَضَ إِسْرَائِيلُ ثَلاَثَ أَصَابِعَ مِنْ فِضَّةٍ فِيهِ شَعَرٌ مِنْ شَعَرِ النَّبِيِّ ﷺ وَكَانَ إِذَا أَصَابَ الإِنْسَانَ عَيْنٌ أَوْ شَىْءٌ بَعَثَ إِلَيْهَا مِخْضَبَهُ فَاطَّلَعْتُ فِي الْجُلْجُلِ فَرَأَيْتُ شَعَرَاتٍ حُمْرًا  

I went to Um Salama and she brought out for us some of the dyed hair of the Prophet.  

دَخَلْتُ عَلَى أُمِّ سَلَمَةَ فَأَخْرَجَتْ إِلَيْنَا شَعَرًا مِنْ شَعَرِ النَّبِيِّ ﷺ مَخْضُوبًا  

Ibn Mauhab also said that Um Salama had shown him the red hair of the Prophet.  

أَنَّ أُمَّ سَلَمَةَ أَرَتْهُ شَعَرَ النَّبِيِّ ﷺ أَحْمَرَ