As well as the arrow for the drop-down combo box, which uses pink for transparency. But see, even with that item, when I try to use the same background color with a different foreground, the transparency breaks - at least in the skin customizer, where it normally works correctly. BUT if I don't mess with the background at all and paint directly on it (which is how I made it green for the GitS skin), the transparency works fine! Aargh!

Why couldn't they have just used bloody .png files? That would have made skinning a whole lot easier and infinitely more flexible.