Praise be to Allaah.
The hadeeth to which you refer was narrated by Abu Dawood, may Allaah have mercy on him, in al-Sunan, from Umm Salamah who said: “When the aayah ‘… to draw their cloaks (veils) all over their bodies…’ [al-Ahzaab 33:59 – interpretation of the meaning] was revealed, the women of the Ansaar came out looking as if there were crows on their heads, because of their clothing.” (Sunan Abi Dawood, Kitaab al-Libaas, Baab fi qawlihi ta’aala: yubneena ‘alayhinna jalaabeebihinna).
The author of ‘Awn al-Ma’bood fi Sharh Sunan Abi Dawood said, commenting on this phrase: “Their veils were likened to crows because of their black colour.”
However, it is not a condition of hijaab that the clothes should be black, but it may be better because it is more concealing. For the conditions of Muslim woman’s hijaab, please refer to question #214.