Weird. It worked just fine for me using the method I posted. Check your page source and see if the color:black is showing up in the <a> tag like I have above. Also, check your stylevar "navbar_selected_popup_body_a_Color" and see if it is modified to white instead of black.
Attachment 106223
I did it by using a template so that I could use the stylevars to get the color from the users css instead of saying color:black.