Check out this liquid that momentarily turns dark green when struck by a UV laser beam:
The molecules in the liquid, called hexaarylbiimidazoles, are known to have photochromic abilities, which means that they change color when blasted with the right wavelength of electromagnetic radiation. Other photochromic chemicals are used to make sunglasses that darken when they are taken outside — into bright sunlight.
When these special chemicals are struck by ultraviolet light, they break in half, forming two colorful and highly-reactive smaller molecules called radicals. Eventually, the radicals re-combine to form the original molecule, and the color goes away. The compound in this liquid reverts to its clear appearance within milliseconds. Read more here.