There's an easy way to figure out what color dyes are in your Halloween candy. That's right - we'll use some science! For this chemistry experiment, all you'll need is candy, water, salt, and a coffee filter.
Grab a plate and put droplets of water at even intervals along it. Put a piece of candy on each of these separate droplets and leave it there for a few minutes, letting the water dissolve some of the dye. Then grab and eat the candy. Using a slender object, like the prong of a fork or a toothpick, transfer a dot of each bit of colored water to a coffee filter. Line up the dots in a row a couple of inches above the bottom edge of the paper. You might want to let the coffee filter dry and then repeat the process, touching the toothpick to the same dot and making it good and strong.
Next mix about an eighth of a teaspoon of salt into three cups of water (you won't need the whole three cups, but this will get the right concentration). Dunk the bottom of the paper in the water, making sure the water line stays below the actual samples. You can either suspend the paper above the water, or fold it so that it's free standing.
You'll notice the water creeping up the paper, soaking it. As it hits the samples they'll run up the paper. Give it a little time, and they'll separate into different spots, or spreads, of color. The water climbs the paper through capillary action. The water is slightly attracted to the paper and so it pulls itself towards the nearest strands, in a process called adhesion. Water molecules are also attracted to other water molecules, yanking them up after themselves as they climb. This is called cohesion.
The combination of the two processes causes the water to climb, and to climb at a certain speed. Different dyes alter this speed, and so they will climb the paper at different rates. So the dyes slowly separate out like runners in a long marathon course. The fastest climb ahead farther and farther, while the slowest get further and further behind. Eventually they'll all catch up if they have enough time and water, so as soon as the first dye hits the top of the paper, or if you just think they're as separated as they can get, haul the paper out of the water and dry it.
Recommended candies are brown m&ms, which separate out into a whole rainbow of color. Also try comparing Skittles and m&ms. Although they share many of the same colors, they're not necessarily made from the same dyes.