Customizing "Lister Style" tabbar and "Folder Tree" border

I have some problems styling some parts of DO. Especially the "Lister Style" tabbar and the border of the tree part seems impossible to style (a background color would be enough for me). Here's how it looks now:

I've seen a styled "Lister Style" tabbar on several screenshots around here, so I think it is not impossible. Can someone tell me how to do it?

Check out the screenshot from that thread. Look at the far top right of the image.

Greetings,
Benjamin

While in Customize mode, right-click the place-holder for the tabs and then turn on Transparent Tabs. That makes them use the toolbar's background as in the screenshot you linked.

Thanks alot!