the way I did it if you see my website:

http://datemeatlanta.com I changed the background from the gray to a green. It was pretty simple. If you have photoshop I recommend just using that. The image you want to work with is

"/templates/tmpl_uni/images/body_backgr.gif"

off of your root directory for dolphin. Change the color or pattern, you can stick with the striped, or do a solid background. You can create your own, as long as you call it "body_backgr.gif" and upload see more to overwrite the existing.

Keep a copy of the original on hand just in case you don't like the outcome, you can always go back to the original and start again.

cheers,
josh