Let's say you wish to create a collage that makes use of images in your catalog that are of visually-similar colors.
With the PSE7 Organizer, similar images can be found "in a snap" (to borrow a phrase from Chuck and Steve's early books):
--drag the thumbnail image(s) from within the Organizer to the Find bar at the top of the Organizer and
--Voila!--the Organizer lists them, by percentage, from most to least visually similar (the below image shows only a fraction of those found by the Organizer)