I was wondering earlier why the predominant color of Islam is green. According to Wikipedia, green is the color of the garments of the "inhabitants of paradise". But, this article in Slate provides a far simpler (additional) reason:
Because it was supposedly Mohammed's favorite color. The Islamic prophet is said to have worn a green cloak and turban, and his writings are full of references to the color. A passage from the Quran describes paradise as a place where people "will wear green garments of fine silk."