Easy to use customizations for the default theme Twenty Eleven--add sidebars back into your blog pages, and quickly change individual color settings.
Login to your blog's Site Admin and go to Appearance >> Theme Extensions, where you can select from the list of options available. Online help is available for all the options. Just click the question mark icon next to the option title you need help for.
When you have changed the settings to your satisfaction, click Save Changes and the requested changes to the theme will be made instantaneously.