Have a look in this thread Plugin for Bullet Threading - #31 by KillyMXI for what you want, the gist further up the thread (linked as a reply from the above post) has the CSS snippet.
Have a look in this thread Plugin for Bullet Threading - #31 by KillyMXI for what you want, the gist further up the thread (linked as a reply from the above post) has the CSS snippet.