Sayyed Mohammad Al-Musawi, Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to... Answered 3 years ago

Yes it is not only allowed but even recommended (Mustahab) to dye the gray beard and gray hair with any color which suits you. Some non Shia Shaikhs claim that black color should not be used. This claim is not authentic and has no evidence. According to authentic Hadeeths, using any color which suits you is allowed.