I now see the green "publish" button in mediawiki.org. However, the "cancel" action has become a red link, rather than a blue link. As everybody knows, a red link is a link which brings you to a 404: you click it only if you want to create the page. The styling is inappropriate for MediaWiki and does not achieve the expected outcome of conveying that clicking the link is a "destructive" action (clicking a red link is usually a constructive action).
"Cancel" should either be a blue link again, or be of another colour, or become a proper button with whatever background is wished.