I saw Ibn Umar dyeing his beard yellow, so I asked him about it.He said, "I saw the Prophet ﷺ dyeing his beard yellow."
أخبرنا يحيى بن حكيم قال حدثنا أبو قتيبة قال حدثنا عبد الرحمن بن عبد الله بن دينار عن زيد بن أسلم
رأيت ابن عمر يصفر لحيته فقلت له في ذلك فقال رأيت النبي ﷺ يصفر لحيته
Bukhari narrated it in wudu, the chapter on washing the feet while wearing sandals and not wiping over the sandals, hadith no. 166, and Muslim narrated it in Hajj, the chapter on entering the state of ihram from the place where the mount sets off, hadith no. 1187, from the hadith of Ubayd bin Jurayj, with this same wording.