[Help] Where is location of this highlight selection in WSB?

The hot/hover/hightlight selection inside black background. As I remember the highlight text itself can't be changed (hardcoded), it's always black text, but the highlight selection can. Just at the moment I can't manage to find out the location to edit this highlight color/image. I did look through entire Complete Guide Customize Theme (pdf which originally came from VirtualCustom) but didn't seem to see this part mentioned (it could be share the graphic image with other location but I've no idea right now).

So anyone? Thanks for reading.