Is it forbidden for a widow to wear black clothes after the completion of her iddah, on the grounds of imitating Christians, and is she sinful if her intention is to express her grief?

It is permissible for a Muslim woman to wear black during condolences, provided that it does not involve imitating non-Muslim women and is not an adornment. Mourning is not permitted for longer than the waiting period ('iddah). What has become widespread in some countries, namely the exclusive wearing of black for mourning and abstaining from other colors, even if they are not adornment, has no basis.