It's OK if it takes you a couple minutes to realize this is genius. And it helps to know the backstory, although figuring it out youself is probably more fun. And the song is called "Figure It Out" after all...
But, if you're the type who loves a spoiler, here ya go:
Director Ninian Doff creates a nifty hidden image trick thanks to a specal blue/red filter placed in front of the lens. Yes, it bathes all the footage in either red or blue, but more importantly: The filter only reveals certain colors. Think of it like old-fashioned red/cyan anaglyph glasses, except instead of creating the illusion of 3D, Doff is revealing hidden messages and images. It's the same gag you've seen in various red reveal tricks you've seen in board games and elsewhere, but transported to video.
Oh, and by the way: You'll notice the video starts with a Parental Advisory warning. So, don't get too distracted by the tricks, otherwise you might forget to miss out on the bloody narrative fun.
