How do I color the Search Box?

Page/site: http://www.todddawsondesign.com/test/matia/
WP: 3.5
ATA: 3.7.10

I want to color the Search box, and for the life of me can't figure out how to do it. I've used Firebug to try to figure it out, but it seems to be beyond my limited skills. Where is the original code for all this? (so I could copy/modify it in css inserts)

I didn't see any other posts on this...

Any help appreciated.