Often times, changing the color code as you supplied above does nothing. You may have to go into the themes .css to change most, if not all, of the themes attributes. The color codes may also be in the .html files so you may also want to look there.

As for reverting back to the old theme, that shouldn't be a problem. Simply delete the theme you have now and upload the older version. Make sure to test the theme in "Your Account" prior to making it the sites default first.