The Messenger of Allah ﷺ said, "The best thing with which you can change gray hair is henna and katam."
أخبرنا يعقوب بن إبراهيم قال حدثنا يحيى بن سعيد عن الأجلح عن عبد الله بن بريدة عن أبي الأسود الديلي
قال رسول الله ﷺ إن أحسن ما غيرتم به الشيب الحناء والكتم
[Its chain of transmission is sahih] Tirmidhi narrated it, Clothing, chapter on what has been said about dyeing hair, no. 1753, from the hadith of Ajlah with this wording, and he said, hasan sahih. It is also in al-Kubra, no. 9350, and Ibn Hibban graded it sahih, no. 1475.