Leaving apart the special case of radial gradients, in Flash it is basically not possible to draw a gradient with 4 different colors in its 4 corners – it’s either a horizontal or a vertical gradient, but not both dimensions at the same time. Explore extra dimensions with the  
Gradient Tween Editor

For a possible use, check out this experiment:

gradient eye

gradient eye tween

see also the tutorial written by Joseph Balderson on CommunityMX.

(originally developed and published in 2005)