There is no report of the Prophet (peace and blessings of Allaah be upon him) forbidding dyeing the hair any colour except black. There is nothing wrong with a woman dyeing her hair any other colour – brown or blond or any other, so long as by doing so she is not imitating kaafir women or immoral women.
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) was asked about the ruling on a woman dyeing her hair any colour other than black, such as brown or blond?
The basic principle is that this is permissible, so long as it does not lead to resembling kaafir women or immoral women, because that is haraam. End quote.