Board Thread:Support Requests - Getting Technical/@comment-1411998-20130907191430/@comment-4018164-20130907202416

They use a 92% transparency. You can apply it using this CSS for monobook (in MediaWiki:Monobook.css): If you also want to apply it on the bottom and left monobook navigations, apply it on the following selectors as well:
 * 1) column-content, #footer, .pBody

For Wikia's bottom navigation, use (in MediaWiki:Wikia.css of course):