Shama-il Tirmidhi
Shama-il Tirmidhi Chapter 006, Hadith Number 002 (045).
Hadith Section/Book: Shama-il Tirmidhi Chapter 06. Rasoolullah Using a Dye
Abu Hurairah Radhiallahu 'Anhu was asked: "Did Rasulullah Sallallhu 'Alayhi Wasallam use a dye?" (for his hair). He replied: "Yes."