Sidebar top group customization

Hi.

I’m trying from some time now to customize the right sidebar top group, in a page with 3 columns layout (left sidebar, main content and right sidebar). What I’m trying to accomplish is to make the right sidebar top in black background color (like the one on the left) and to get rid of the text inside.

There it is: https://conceptie.ro/prtscn_right_sidebar.jpg

Pls help. Thx!