how to select different colorbox styles for different content types in drupal 7?
There is no way to do it from admin UI. 
Formatter settings also has no option to select style for current image display.

But you can try the following:

function [themename]_preprocess_node(&amp;$vars) {
  if ($vars['type'] == 'node_type' &amp;&amp; $vars['view_mode'] == 'full') {
    variable_set('colorbox_style', 'stockholmsyndrome');
  } else {
    variable_set('colorbox_style', 'default');
  }
}


Yep, it's dirty hack, but it can helps... maybe... =)