The theme colors are always near the bottom right before the responsive section of the css…..but you’ll need to do a little bit more than that to create another color scheme. You can Google how to do this and a lot of tutorials should show up. Here are a few –
http://www.briangardner.com/code/create-color-style-options/
http://www.wilwebs.com/2013/02/how-to-add-color-schemes-to-a-genesis-child-theme/
http://wpsites.net/web-design/change-color-theme-genesis/