Google AdSense Ad Unit Changes Made Easy With New Feature

"This new ad management feature means that your ad unit settings (such as colors and channels) for new AdSense for content ad units will be saved in your AdSense account every time you generate ad code. Then, if you'd like to change any of these settings in the future, all you do is make the update within your account -- you'll no longer need to manually replace the ad code on all of your pages."