Virtuemart category modul - css

Hi!
I would like to colorize the active menu item of virtuemart category module in my Your Shop template and it would be nice to bring inner the submenu items...
Could anybody tell me, how should I change the css files in this case?
Thanks!

Hi

Can You please show me what You have in mind exactly ? An url to the exact page would be great too, so I'll be able to tell some css classes right away.