This enables custom links that can open forms and paths in a Colorbox. Add the class "colorbox-load" to the link and build the url like this for forms "/colorbox/form/[form_id]?destination=some_path&width=500&height=500" and like this for paths "[path]?width=500&height=500&iframe=true" or "[path]?width=500&height=500" if you don't want an iframe. Other modules may activate this for easy Colorbox integration.