At the time of the Prophet there was no difference between the clothing of the Muslims and that of the polytheists

At that time the Muslims didn’t have uniforms. For this reason the Muslims shouted slogans (e.g. “Ahadun Ahad (He, the One, is One!”) that they had previously determined, in order to distinguish their brothers from enemies in the crowd. The Prophet later warned, “Oh Muslims! The angel, that Allah has sent you for help, bears signs. Therefore also obtain for yourselves signs. Those that could obtain them, appended their head coverings and helmet parts of wool for increment. (Tafsir at-Tabari, Tafsir about Al Imran 125; Kanzul-Ummal, V, No. 5349; Muhammad Hamidullah, Hz. Peygamberin Savaşları ve Savaş Meydanları (Battlefields of the Prophet Muhammad), translated from Salih Tug, Yagmur Puplications, 4. edition, Istanbul 1991, p. 70-71).