In the dashboard, I went to Appearance, then Graphene Options, then Colors, then Content Area. I then cleared the color code out for Posts & Pages Content Background, picked a color using the color picker, and clicked on Save All Options.
Next, I repeated the above process with Content text.
Finally, I clicked Save Options at the bottom of the page.
After doing all of this, I visited the site, and discovered that the colors had not changed. When I went back to the Colors tab in Graphene Options, I discovered that the colors had reverted to their original settings.
By the way, I am using a laptop, running Windows 7, and using the Chrome browser.