Comment 4 for bug 1031520

Looking at lines 82-128 of http://bazaar.launchpad.net/~marlin-devs/marlin/marlin-0.5/view/head:/src/View/OverlayBar.vala , it appears that the element in question is referred to as a ".floating-bar", and is set by default to have a light gray background color. I'll have a go at trying to implement a fix in gtk-3.0/apps/marlin.css.