A woman is permitted to use brown hair dye provided the dye is permeable (water can pass through).
If the dye contains any Haraam ingredients, it should be avoided as other Halaal alternatives are available. Nonetheless, even if she uses a dye with Haraam ingredients, her Salaat will be valid if her hair is washed after application.
and Allah Ta’ala Knows Best
Mufti Muhammad Kadwa
FATWA DEPT.