yah, you would have to modify two things:
1) the postlist.tpl would have logic to add to the class based upon {if $postrow[topic].announce} kinda dealio. so you'd append an extra class to things like: class="{$postrow[topic].color}newintopic" and make it class="{$postrow[topic].color}newintopic announcey"
do that for each of the td's in the row basically
2) then add the class in your extra css like .announcey {background: hotpink;}
*poof* done
