بسم الله الرحمن الرحيم
Yes, it is lawful. However, during some special days the Shia wear black clothes in particular, so in order to avoid their resemblance during those days one should not wear black clothes like them.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.