(24) بَاب اسْتِحْبَابِ خِضَابِ الشَّيْبِ بِصُفْرَةٍ أَوْ حُمْرَةٍ وَتَحْرِيمِهِ بِالسَّوَادِ
Jabir b. 'Abdullah reported that Abu Qubafa was led (to the andience of the Holy Prophet) on the day of the Conquest of Mecca and his head and beard were white like hyssop, whereupon Allah's Messenger (ﷺ) said:
Change it with something but avoid black.
Reference: Sahih Muslim 2102 b
In-book reference: Book 37, Hadith 124
USC-MSA web (English) reference(deprecated numbering scheme): Book 24, Hadith 5244