The University of Southampton in the United Kingdom and the Institute of Plastics in Darmstadt, Germany, jointly developed a color changeable plastic film. This film combines natural optical effects with artificial optical effects, and is actually a new way for objects to change color accurately. This kind of plastic film is a plastic opal film composed of plastic pellets stacked in three-dimensional space. It contains tiny carbon nanoparticles in the middle of the plastic pellets, so that light is not only in the plastic pellets and the surrounding material. The fringe area reflects, and is also reflected on the surface of the carbon nanoparticle filling between these plastic pellets. This greatly deepens the color of the film. As long as the plastic pellets are controlled in size, light materials that scatter only certain spectral frequencies can be generated.