[vB5] Just a minor graphics fix

[Gota]

Something I want to change is the white thing you can see in the preview image. It's just a flat white color but I want it to look a bit better, like the black left and right of it (the navbar). I basically want to have the active tab look a bit more fitting together with the black navbar.

[Wayne Luke]

That is controlled by style variables. The header_tab_*_active style variables to be exact. They are found in the exact same location as the style variables for the inactive tabs that are already modified.