It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "A Muhrim (one in the state of Ihram) cannot wear a shirt, trousers, turban, or socks, except if he does not find shoes. Whoever does not find shoes should cut the socks below the ankles and wear them. Similarly, a cap or any cloth upon which wars (a type of grass) or saffron has been applied, a Muhrim cannot wear that either, except if it has been washed."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5003