Is it permissible for a woman to dye her hair, and what is the ruling on that?

It is permissible for both men and women to dye their hair, especially if it has turned gray. It is preferable to use henna and katam. Dyeing hair black should be avoided by both men and women. It is permissible for a man to dye his own hair, and for a woman to dye her own hair, or that of her husband, or her mahrams.