Does anybody know of any circle filling algorithms that fade colors?

I want to draw a filled in circle that in the center is white and fades to light blue and then fades to dark blue by the outer edge of the circle.

I have an algorithm to draw a circle.....but I need some type of algorithm to fill a circle, especially the way I want to do it...and a circle filling algo is not near as easy as a rectangle filling algo....

so anybody know of any?