Move so that you are looking at the water with the sun behind you. Spray harder or softer and higher or lower until you see a rainbow. Try changing your position so that the sun hits your water from a different angle. Or try having your partner spray the water while you view from different angles and distances. If you are successful, note the order of the colors.
Light is an electromagnetic wave of energy.
Some electromagnetic waves have higher energies than others. The whole range is called the electromagnetic spectrum. Waves in this spectrum include X-rays, microwaves, radio waves, visible light, and others. The waves of visible light, which is what we can see, are in the middle of this spectrum. Their energies are lower than those of X-rays, but higher than those of microwaves and radio waves.