Is it permissible for a Muslim to dye his hair with something other than henna?

Changing gray hair with a color other than black is commendable. Dyeing it with pure black is forbidden for both men and women, based on the Prophet's (peace be upon him) saying: "Avoid black," and due to the severe warning for those who do it. It is permissible to mix black with another color so that it does not remain pure black.