add color with CSS to separate menu

I am adding a custom menu to the sidebar. Highend allows the placement of four menus, but the sidebar is for widgets. The widget I chose creates a custom menu in the sidebar, and it works fine. The color of the menu is white, however, and I find no option to change this. My guess is that the global settings for the theme that color the four menus do not support the custom menu widget I use in the sidebar. I have been attempting to change the color by entering values in the CSS Classes window of the individual menu entries. No luck. (see screen shot). Do I have the CSS command wrong, or is there another way? I want to change the background color of the menu items, leaving the type black.

Thank you for your help.