I don't know who thay are, but their kit is made from Electroluminescent wire (or EL wire, or Glowstring if you're searching for it). Ikea used to stock it in 2 meter lengths with a battery pack.
Hubby and I added it to our evening clothes for the Snake Pit and we got waved in past the the queue - someone assumed we were performing there.
they could change the colour and shape as well, btw, presumably they had the controls in one of their hands - changing from smiley to angry or evil face, maybe more faces, and activating the devil horns as well. that doable you think?