If I could successfully skill 9 points into all energy types, I would dedicate one of my toons to having a rainbow build with an annoying star cruiser setup. Although, a rainbow turret scatter volley build would look cooler :p
I've run a rainbow build of both types...kinda fun and silly! However, the greens of disruptors and plasmas kinda blend together like the red-orange of the Phaedra and the reds of anti-protons. Still cool, though!
Throw in some chroniton torpedoes because of their multi-color explosions and you're set!