Islam Q&A writes concerning a woman dying her hair:
With regard to changing it with different colours of dye, the basic principle is that it is permissible, unless it is done in the manner of kaafir women or immoral women, in which case it is forbidden for that reason, because the Prophet (peace and blessings of Allaah be upon him) said: “Whoever imitates a people is one of them.” (Narrated by Abu Dawood, 4031; classed as saheeh by al-Albaani in Irwa’ al-Ghaleel, 5/109).
In my case, I bleached my hair blonde before reverting to Islam (from being irreligious), now I'm concerned it's not Muslim-y enough. It's safe to say it's not a modest color at the moment--it stands out and people ordinarily assume I'm not a Muslim. I'm thinking I should dye my hair darker, to a more natural and less noticible color. At the same time, I like my hair color, so wouldn't want to change it uncessarily. (NB. I'm yet to do hijab outside of prayer; I'll try in a few weeks when I go to Iran. NB2. I don't have a husband.)
Question: What hair colors are precluded for Muslim women?
It seems like the answer will be more complicated than "colors X, Y, and Z". So some guidelines and examples which would be forbidden would be helpful.
(The question Dyeing our hair in Islam addresses the question of whether or not hair dying is permissible.)