I don’t know css. I have found the code snippets to change the background color of the menu but don’t know where to place it. I tried to put it in the Quick CSS of the Enfold theme options but it had no effect. The snippet I found is:
.header_color .main_menu ul:first-child > li > a { color: #000000; } /* color of main menu items */
.header_color .main_menu ul:first-child > li a:hover { color: #FF0000; } /* hover state of main menu items */
.header_color .main_menu ul:first-child > li.current-menu-item > a,
.header_color .main_menu ul:first-child > li.current_page_item > a { color: #FFFF00; } /* color of active menu item */