Add food coloring to your column.Remember how we told you that oil and food coloring won’t mix? That’s because the food coloring has a higher density than the oil. Try putting a few drops of food coloring onto the top of your column. What happens? You should notice the food coloring slowly moving through the oil in streaks and then settling into the water layer. Because the food coloring isn’t as dense as the syrups, it should stop and rest on top of that layer.