[TheLastSuperman]

Try adding this to additional.css template in your custom style:

#blogtagmenu_1_menu, .ajax_tag_edit_container {
background:#000000 !important;
color:#ffffff !important;
}

Change #00000 from black to your bg color for that area and change #ffffff to whatever font-color you want.

Worked for me on 4.2.1 but let us know .