#005577 (dwm blue) by Firefox user 10808110

Use this custom css to disable the white overlay:

<code>
@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);
#navigator-toolbox > toolbar:-moz-lwtheme {
background-image: none !important;
box-shadow: none !important;
border-top-color: transparent !important;
}
</code>