I don't see any easy solution for this. You'll need to edit contextual-related-posts.php
You could try something like this for now:
Line 104: change from:
$output .= $crp_settings['before_list_item'];
$output .= str_replace("%posttype%",get_post_type( $result->ID ),$crp_settings['before_list_item']);
Then in your Output Options tab for "HTML to display before each item", you can change it to
This should replace %posttype% with the actual post type i.e. post or page and you can apply your CSS styles then.
Do let me know if this works for you.