Women dyeing their hair for the purpose of beautification
Question

                Is it permissible for a woman to add colours to her hair unnecessarily for the purpose of beautification?.
Praise be to Allah.
    The basic principle concerning things other than acts of 
    worship is that they are permissible. Based on this it is permissible for a 
    woman to dye her hair if she wishes, unless it is black dye that is used to 
    conceal grey hairs, which is not permitted because the Prophet  (peace 
    and blessings of Allaah be upon him) enjoined changing grey hair but he said 
    “avoid black”; or if this dye is something that is used only by kaafir women 
    such that if this woman was seen, people would say that she is a kaafir 
    woman, because no one uses this dye except kaafir women. In that case, it is 
    haraam for a woman to dye her hair with it, because the Prophet  (peace 
    and blessings of Allaah be upon him) said: “Whoever imitates a people is one 
    of them.” If the dye is free from these two elements, i.e., black to cover 
    grey hairs and dye that is used only by kaafir women, then the basic 
    principle is that it is permissible, so the woman may dye her hair if she 
    wishes. End quote. 

    Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him).