Rotating the palette as Hellfire said will provide the fastest result, but here's an idea I had.
If you generate the voronoi pattern bigger than the screen and you shade or fill in the black areas between the lines you could apply a sine wave across the horizontal plane of the image, adding blended vertically sined lines accross the top of the image (this would help to disguise that it is just a sined and cycled picture), this would be a really good way of cheating an excellent psychedelic plasma pattern.