This is the Rainbow Roller, a paint roller that paints in rainbows, provided you fill it up properly. There is an Instructable of how to build your own right HERE. Alternatively, feed a unicorn a bunch of beans and laxatives and let it paint rainbows for you. Just make sure to wear a respirator if you're letting it paint indoors though, because, unlike Skittles, it's not going to be the kind of rainbow you want to taste or smell. After it dries tell anyone who comes over it's candy flavored wallpaper and get them to lick it.
Keep going for a couple more shots and a video.