The Messenger of Allah ﷺ said, "The best things to use for changing this gray hair are henna and katam."
حدثنا عبد الرزاق أخبرنا معمر عن سعيد الجريري عن عبد الله بن بريدة الأسلمي عن أبي الأسود
قال رسول الله ﷺ إن أحسن ما غير به هذا الشيب الحناء والكتم
Its isnad is sahih, and its narrators are trustworthy and well known. The hadith was narrated by Abu Dawud (4/85, no. 4205), Tirmidhi (4/232, no. 1753), who said, "Hasan sahih," Nasai (8/139, no. 5078), and Ibn Majah (2/1196, no. 3622).