Just go into the style.css file under the theme and change anything you want. Just about everything can be customized there, colors, fonts, spacing, etc. I use Dreamweaver and load a localhost copy so I can inspect everything visually and then jump right to the code that controls it. Beats the heck out of searching through code for it. The greenish bar on the home page is .slogan-wrap, and the bar on the other pages is .page-title-wrap.
Then just use other colors. I find colors at this site http://www.colorhexa.com/
I tried a child theme, but didn’t work properly – sure it’s my failure even though I used WP guidelines, so I just edited the theme file, keeping backups in case I have problems.
Hope that helps.
Daniel