Veg oil, water, alka seltzer, food coloring, and a bottle. Fill a bottle 2/3 with veg oil and 1/3 with water (keeping in mind to leave 1" at the top). Add 10 drops food coloring. Add 1 alka seltzer (broken in a few pieces, adding one piece at a time - when first piece stops bubbling, add next) and watch the colors.
Milk Art. All you need is milk, food coloring and dish soap. This year in Chemistry I got to test out this project, but my group did it wrong and it didn't come out right. I would love to try again and make a complete piece of art out of it. The colors flow however they want and you can't control it. It's art just the way it is made.