Hi,
You can use Firebug (for Firefox) or Developer Tools (for Chrome) to determine what CSS is being used for what elements.
If i tell you the CSS file, it won't help you, because there are like 2000 lines in the CSS file. Then you are gonna ask me "What line?"
You should better take a look at this topic:
www.flexiblewebdesign.com/forum-virtuemart-2-template-puremart-support/342-using-firebug-for-customization-or-troubleshooting
this will also improve your web development knowledge. I highly recommend you to go over this topic and learn how to use Developer Tools of browsers.
Regards.