Bahr bin Nasr said that Imam al-Shafi'i (may Allah have mercy on him) used to dye his hair.
(b) Sulayman bin Shu'ayb al-Kaysani said: I saw Muhammad bin Idris al-Shafi'i (may Allah have mercy on him); he used to dye the hair of his beard with pure henna.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسم والنشوز / 14826