It's real, I've seen that once before in a documentary of some sort, not sure why I was watching it. But I havn't seen it in reverse, or slow-mo. I saw an experiment where they took a cuttlefish (also capable of colour changing), and put it in a pool of red rocks, the cuttlefish subsequently turned red, then they tok the same animal and put it in a pool of gray rocks, the cuttlefish turned red again, it turned out that cuttlefish are apparently colour blind, and the red and gray rocks apear as the same shade of gray in "black and white." I think an octopus is a bit more sophisticated than a cuttlefish, but interetsing nontheless.
That's really cool. We, as humans consider ourselves to be superior to everything, but we still have a lot to learn from nature.