There is no requirement for women to wear white clothing during احرام. Unlike men, who wear two specific white unstitched garments (izar and rida'), women have no prescribed color or specific garment for احرام. A woman enters احرام in her regular modest clothing, which may be of any color — black, green, blue, brown, or any other color. The widespread misconception that women must wear white or a specific color has no basis in the Sunnah.
Sheikh Ibn Baz stated that a woman may wear whatever she wishes of her regular clothing during احرام, provided it is modest, covers her body properly, and is not tight-fitting, transparent, perfumed, or resembling men's clothing. He noted that wearing overly bright or flashy colors that attract attention is disliked, but there is no prohibition on any particular color.
Sheikh Ibn Uthaymeen confirmed that the احرام restrictions on clothing apply specifically to men — the prohibition of stitched clothing, head covering, and specific garments. Women's احرام is their regular clothing. He advised women to avoid wearing all-white during حج because it can be transparent, attracts attention among the crowds, and may lead to confusion with men's garments. He considered darker, modest colors to be more appropriate for women during the حج.