Islam has not imposed any particular type or color of cloth for Hijab. The main objective of Hijab is to cover the Satar, so that there is protection from troubles, indecency and immodesty. In the light of this, it is necessary that some broad guidelines of Hijab be observed:
1. The Hijab should be such that it should cover the whole body from the palms to her toes.
2. It should be so loose that it should not disclose the structure and outline of the body.
3. It should not be so thin and fine that the complexion of the body is visible.
4. It should be not resemble the particular clothes of the people of other religion, as there are strict warnings for resembling the people of other religions/faiths.
5. The Burqa should not be attractive-looking or have any attractive patterns, designs, etc. as the objective of Burqa is to shield oneself from the gaze of the non-Mahram and not to invite it.
In the Hadith, women have been prohibited to wear attractive clothes while going out of their houses. As given in the Hadith in Sunan Ibn Majah, Hadith No. 3991;At Targhib Wat Tarhib, Vol. 3, Pg. No. 38:
Translation of Hadith: The Holy Prophet (Sallallahu alaihi wa sallam) said: O people! Do not let your women wear beautiful clothes and come before non-Mahram men.
6- Also, the Burqa should not be similar to the clothes used by men in its design, stitching, etc., as it is prohibited for men and women to resemble each others' dress. It is given in the in Hadith:
Translation of Hadith: The Holy Prophet (Sallallahu alaihi wa sallam) has cursed the man who wears the clothes of women and has cursed the woman who wears the clothes for men.