Testing around ... you could do something like this. A Custom HTML/PHP block -> Content Type (PHP) with code:
PHP Code:
$light_or_dark = ($vbulletin->userinfo['styleid'] == 80 ? 'light' : 'dark');
$output = "<center><iframe src=\"http://www.facebook.com/plugins/likebox.php?href=http%3A%2F%2Fwww.facebook.com%2Fpages%2Fmetallifukincacom%2F139184612825288&width=205&colorscheme=$light_or_dark&show_faces=true&border_ color&stream=false&header=true&height=230\" scrolling=\"no\" frameborder=\"0\" style=\"border:none; overflow:hidden; width:205px; height:230px;\" allowTransparency=\"false\"></iframe></center>";
return $output;