How can I recreate this iridescent effect?

You can kinda fake it by manipulating separate channels so their pixels don't line up any longer, i.e. moving parts or blurring elements. Could involve tons of selections and many, many duplicates of the layers with blending modes. Refractive dispersion/ diffractions are complex. Look up some "chromatioc abberation" or "video glitch" tutorials for a basic idea. If the shapes aren't that detailed you can also of course simply paint over the many hues using brushes with very low opacity and set to a blending mode like Overlay or Color.

Mylenium