Milan design group Carnovsky created what is probably the most psychedelic fun wallpaper you'll ever see today (without having to ingest anything):
Three overlapping and primary-colored patterns are placed on the wallpaper panels and, in normal light, create some major visual discord. But here’s where the magic happens: Shine a red, green, or blue light on the walls, and different patterns are isolated and made visible. Each colored light reveals its own set of images.
Link | Larger photos at Carnovsky's website
and it does work really!
the red photo shows it fine, and the blue although blurry kind of gives an underwater effect with the sea creatures.
where was this?