>-sure, but weirdly the effect has to be wavelength dependent, but there are no color fringes.

I do think you can get colour fringes in some circumstances. Try doing it in a dark room with a bright light coming through a small gap (e.g. between curtains). Like:

                                |
                                |                    (dark room)
                                |

    light source - - - - - ->- - - - - - - - - ->- - - - - - ->- - - - - - - - - ->  eye
                                                                       |
                                |                                      |
                                |                                      |
                                |                                    finger
                        small-ish gap (1-5cm)

(not to scale)

IIRC you can get colour fringes between the finger and the top edge of the gap behind it.

EDIT: I just tested it, there is definitely a rainbow spectrum between the finger and the gap. The gap side is blue and the finger side is red. Not sure if this is the same effect as the article though.