You didn't mention the browser you use, but Firefox offers a Web Developer Toolbar that can show you the specific css that affects a given part of the viewed page, if that would help. When activated you just highlight the area you'd like to change and it will show you what to edit in the css. It will let you edit it while you view the page so you can play around with it (without actually altering your css file) until you like the results and then copy it from the viewer and paste it into your css file. Safari has a similar toolbar but I haven't used it as much.
If you do a lot of WordPress sites I suggest using Artisteer. The interface lets you create your own themes choosing colors, fonts layouts, buttons, everything. You can use it with Wordpress to build sites that don't look anything like a WP theme.