I found the following link extremely helpful in changing background and font colors at most levels of the sf menu:
http://themeshaper.com/forums/topic/help-with-css-styles-for-drop-down-menus-in-thematic-09#post-2235
However, I am still stymied for the font color at the top level. I have added a background for the top level only. Changing the font color in that same selector didn't work, so I added a 2nd selector to address the color only. But that didn't work either. All of the "hover"s and "a"s work just fine at all the levels, but I want to have a white font color over the background graphic that I've used.
I would greatly appreciate your help with this.