For properties that deal with color, the Particle System makes use of the Color and Gradient Editor. It works in a similar way to the Curve Editor.
The color-based properties will have a pull down menu on the right hand side, where you can choose between:
Gradient: The gradient (RGBA) will vary throughout time, edited in the Gradient Editor
Random Between Two Gradients: The gradient (RGBA) varies with time and is chosen at random between two values specified Gradient Editor
Page last updated: 2013-02-18