The Grand Ayatollah Sistani has answered a question about the ruling on wearing black clothes in the mourning of Hazrat Seyyed Al-Shuhadā (A.S).
According to Pakistan.shafaqna.com, the text of the question and answer were as follows:
Question: Is the ruling on wearing black clothes in the two months of Muharram and Safar, Mustahabb (recommended) or Makruh?
Answer: It is decent and appropriate and is not Makruh.