If you are using Firefox, the Web Developer and Firebug add ons are indispensable for finding what things are, where they are, and other great things.
I made my gifs here: http://highpowergraphics.com/bannerbuilder/
You need to find the original gif and find the name, and size. Then build your image using that site. NOTE: You will need to put some text in one of the text boxes to get it to work...just use the same color as your background so it won't show, and it wont do any blending of colors.
Don't forget to size it the same as the original, and save it as a gif. Save it to your computer, and upload it to your server.
The green bars look to be
Code:
url(../images/tile_back.gif) and is 11x30
So that tells me to make a gif 11x30 named tile_back.gif in whatever color you want.
Good luck.