via the Big Picture
How Indians celebrate the change from winter to spring. The celebration is said to represent the triumph
of good over evil. As the tale goes, a demoness Holika tries to kill the son, Prahlad of the demon god, Hiranyakashyap, for not worshipping his father. Instead Holika, the demoness goes up in flames and here on Hindus celebrate each year. Bonfires and effigies lead off the celebrations with the color wars to follow.
Evidently you can make natural holi color at home...