yah Giz is right. there are no new styles in the style editor. what i was saying is that you can add it yourself to the Extra CSS portion and take advantage of the 7.3 tpl that accommodates you, if you choose to..
now for 7.2.2, all you have to do is edit postlist.tpl and just check for "{if $postrow[topic].announce}" in the post loop ("section") and then decide to add your chosen extra class to style those rows..
/templates/default/postlist.tpl .. *poof* voila
