I have Superfish in place and I do like it. There are several styles that you can choose from in the block config for SF. They are OK but I want to go with a fairly generic one that I can alter to suit my tastes. So, I have chosen the default style. This uses the CSS file called default.css located in sites/all/libraries/superfish/style
I take that CSS, copy it and put that copy under the name of sf.css and place it in:
/var/www/html/sites/all/themes/adaptivetheme/docresource/css – this is my drupal install
location and my SUBTHEMEd version of AT_CORE.
I then edit the .info file of my subtheme and add the reference to the new CSS file I have added. Then, I flush the cache and check the CSS being used via Firebug.
You can see that the CSS file referenced is the new one that I have created. Now, I can change all the SF CSS that I want.