April 17th, 2012, 11:18 AM
Joined: Sep 2010
| | I may be a bit late to this party but here goes
Black was traditionally used by the Prophet's army, and later on by the Abbasids.
White was traditionally used by the Ummayeds.
Green was used by the Shia Fatamids (Green being the colour of Ahlulbayt, the Prophet's household)
And if you're wondering about the Kharijites, they used red