When the windows display scheme is not equal to the Windows Standard and the bit depth is 8 bits colors with alpha values appear grayish. To reproduce :

Control Panels -> Display -> Appearance -> Scheme -> Desert
Display -> Settings -> 8 bit or 256 Colors
run Java2Demo see Mix.Balls or anything with a alpha will appear with a grayish color.

beta4-K.

Colors look okay with all other bit depths.