Like Iris said above me; if it's the shadows color you wish to change. Like making the black turn to white. There should be a back with the color that it will become on the tab if the filter itself. Just click it and another tab will pop up with the color palet.
I'm yanking this out of my memory. But if it's the background color of the background that the shadow drop layer is above. All you have to do, I belive is use the hue, light, and saturation(I might be wrong about it. Lacking GIMP in my mind). Go to the hue bar and you can change it there. Which is under the color filter catagory a believe. That's how I would change my colors. It's more rich and vibrant that way.
Worldy, I'm quit confused by what you mean.
