If you have some spare Skittles lying around the house and you don't want to eat them, then this science trick is a perfect solution.
Arrange the Skittles (this will also work with M&Ms) in whatever design you like in a dish or cup (depending on how many you want to use) and then slowly pour some warm water over the candies. The shell of the Skittles will eventually begin to dissolve, and it'll take the food coloring with it. The result, depending on how you arranged your Skittles, should look like the video above, a rainbow of colors coming together but not blending together.
The science behind it is pretty simple: water stratification. The sugar content from each candy is roughly the same, so each dissolved bit of sugar acts as a barrier, preventing the fluid from blending together; the food dye just makes this process visible to us. Pretty neat, huh?
Over time, the colors will begin to blend as the actual candy itself begins to break down and different amounts of ingredients shift the densities of the water. One blogger prepared two more bowls of Skittles and water the night before doing the rainbow dish experiment with her kids, and the results are, well, let's say they're just as scientifically interesting but significantly less pretty than the rainbow dish.