Sayyiduna Ibn Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him), in explaining the saying of Allah Almighty "marked" [Surah Al Imran: 125], said: "That is, bearing distinguishing marks. On the day of Badr the mark of the angels was black turbans, and on the day of Uhud it was red turbans."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11421