I'd like to have the menu background color different then the menu items.
I've tried this code:
div#menu1 {
background: #beaf7f;
}


in css inserts, it didn't work.
site is www.bucstop.com

recheck your CSS Insert, you don't have the ';' after 'beaf7f'

Your code is right however for the default left aligned menu the ul.rMenu inside the div#menu1 spans the whole layout width and the background color of that is different

div#menu1 ul.rMenu {
background: #beaf7f;
}