I have been using firebug for at least an hour to try to figure out what is controlling a grey background color in a menu.
I am using a menu component. And to help me track down the module I added an "additional" red background -- just as a visual way to help me track down the elusive color.
The hover color is grey. I think it is #D1D1D1 but I am not sure.
In my next comment I will post the link to the development page.