Themes: How to change the background of that pop-up like window?

Hello. In what file there is the settings for those op-up like window thingys? I don't know how to name them and it's kinda hard to look over all xml files. Where can I change the colors of those window-thingys?

I wan't to prevent that nasty overlapping thing like there is on that theme here:



And this one


Where to edit the background colors and stuff for...

Themes: How to change the background of that pop-up like window?