Here is a pretty easy setup to play with.
Change your material to have a custom color on the edge of the fresnel fall-off. I did this with two diffuse nodes, one grey for the main portion of my objects, and one a green color, and then used a mix node with the factor being my fresnel output.
Play with the Fresnel value to your liking.
"Green-Screen" out your green in the compositor with chroma key.
"Alpha Over" this chroma keyed image under a multi colored image (could also be an image strip for some pretty cool effects), by a factor being driven by the Matte output of the Chroma Key.

If you want to fine tune this, then start playing with the Cutoff value in the Chroma Key Node.
Note that I dropped this from 10° to 0.71° and got this result. Ignore the brightness, I just upped my ambient occlusion all the way up.
