Maybe for a RTS?
Very Simple Idea:
-Create a second "PANEL"
-bitmap is the Button (the same only in grey)
-place it over the button
-make it invisible
-give the layer a higher Value as from the Button
-create a Function with a simple Var (lets Take X)
-create a If(x==1){My_Grey_Button.visible=on;} in this Function.
Ready to use...
cYa Sebastian
Tutorials:
[Blender]Terrain creation ENG/GER
[Blender]Low Poly Tree Modeling
[GIMP]Create a Texture for Terrains
CLICK HERE