It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that a man asked the Prophet Muhammad (peace and blessings be upon him): "O Messenger of Allah! What clothing can a person in the state of ihram wear?" Or he asked: "What clothing should a person in ihram avoid?" The Prophet Muhammad (peace and blessings be upon him) said: "He cannot wear a shirt, trousers, turban, or leather socks, unless he does not find shoes. Whoever does not find shoes should cut the leather socks below the ankles and wear them. Similarly, a cap or any cloth dyed with wars (a type of grass) or saffron, a person in ihram cannot wear that either."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4835