I downloaded the qPloneDropDownMenu product, and installed it on my site.  I was able to adjust the colors and widths of the drop-down menus, but I seem to have lost the ability to designate the color of my selected tab.

I used #portal-globalnav li.selected a {} in my ploneCustom.css to no avail. 

Any suggestions?

This is because the qPloneDropDownMenu-0.1.x series has fixed HTML from its configlet as menu and it is not generated (as default plone tabs are).

In default Plone, while changing section of the site, the .selected class changes list item it is attached to. In qPloneDropDownMenu-0.1.x it is not, thus it is not possible to do any CSS highlighting of section visitor is in.

With current version of product you'd have to rewrite the code that generates your tabs (and embedded menus) to be mixture of default Plone tabs and your sub-menus. This feature was too complex for v0.1 of product and it will be available in v0.2 (you can test it from SVN, but we do no guarantee the site will be working if you upgrade to 0.2 release as there is major rewrite of 0.2 undergo).