Category CSS Class 0.1
If this isn't working for table view, you can fix that by opening "applications/vanilla/views/discussions/table_functions.php", search for "// $Sender->FireEvent('BeforeDiscussionName');" and delete the two slashes from the start of the line.
If you create a css file called "/plugins/CategoryClass/design/CategoryClass.css", it will automatically be loaded.
Plugin was created because of that discussion
Sources on GitHub