The Squid giant axon! The squid has 3 different chromatophore colors: Brown, Red, and Yellow. Each chromatophore has tiny muscles along the circumference of the cell that can contract to reveal the pigment underneath.
“We used a suction electrode to attach to the squid’s fin nerve, then connected the electrode to an iPod nano as our stimulator. The results were both interesting and beautiful. The video below is a view through an 8x microscope zoomed in on the dorsal side of the fin.”
More information at http://news.backyardbrains.com/2012/08/insane-in-the-chromatophores/
Human beat box to a cockroach leg. Here is a TED talk that explains simply the process of the electro-stimulation through the chromatophores by using music to stimulate a cockroach leg. This makes working on mice seem not as bad.