Food color mixes faster in warm water than in cold water. Molecules in a liquid have enough energy to move around and pass each other. This is why water can flow and take the shape of the container you pour it into. Warm water has more heat energy than cold water, which makes the molecules in warm water move faster than molecules in cold water. The food coloring you add to the water is pushed around by the water molecules. Since the molecules in warm water move around faster, the food coloring spreads out quicker in the warm water than in the cold water.