You need to find out which classes/ids to style. Use firebug or some other browser developer tool to inspect the element you want to style, then check the class or ID and use CSS selectors to make the changes.
Google's CSE page allows you to do some styling, but as suggested above, when you put your page together, simply run through a search and view the results by looking at the source code (view source) by right clicking somewhere in the page. You'll find all of the elements there, there IDs and Classes. Then, just build your own custom CSS to target these elements with the styles that you choose.
A good example of customizing Google Custom Search Engine is here on this site. Try using at Daniweb's search feature. You will see that the page is customized to fit this site's design.
Have you looked at the search page results on this site? That is a good example.