What is the ruling on dyeing hair a color other than black during menstruation, and does it affect the validity of prayer?

A woman is permitted to dye her hair any color except black. Hair dye is permissible whether she is menstruating or in a state of purity. If the dye forms a layer that prevents water from reaching the hair, then ritual purification (ṭahārah) is not valid unless it is removed. However, if it does not form such a layer, then it does not affect ṭahārah. Ibn Qudamah said: "If one dyes his head with something that covers it, or plasters it with mud, then wiping over the dye or mud is not sufficient… because he has not wiped the obligatory part."