Shafaqna (Shia International News Association) – The Grand Ayatollah Sistani answered some questions regarding black cloths. According to Shafaqna the question and answer are as follows:
Question 1: Is it permissible to drape a mosque with black cloths?
Answer: If a mosque is draped with black cloth, or covered with a marquee in preparation of Majlis to be read there, there will be no objection to all that if they do not have any harmful effect on the mosque, and if it does not obstruct those who come to pray.
Question 2: Is it permissible to wear black Ihram?
Answer: It is discouraged to wear ihram in black cloths; as a matter of precaution, this color must be avoided and it is preferred that the ihram be of white cloths.
Source: Ayatollah Sistani