@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

/* this part adds more spacing around each menu */
/* comment this part out if you don't want it */
toolbox#navigator-toolbox > toolbar > toolbaritem > menubar > menu {
  padding-left: .8em !important;
  padding-right: .8em !important;
}

/* this part does the rollover background changing */
/* you can change background color to whatever you want */
/* the background image only works with Aquatint */
toolbox#navigator-toolbox > toolbar > toolbaritem > menubar > menu:hover {
  background: url("chrome://global/skin/custom/plaintabs/body-selected.png") #acacac !important;
  background-position: 0 -2px !important;
  color: black !important;
}