Researchers have produced thin films having bichromatic properties that can be deposited on any transparent or translucent substrate (glass, ceramic, polymer, etc.), the two-color effect being independent of the observation angle. Thus, when a light source is placed behind the material, it will appear a certain color, called "transmission color"; and when the light source is located on the same side as the observer (ie in front said material), it appears in a different color so-called "backscattering color". More particularly, researchers have developed a process for producing a bichromatic film comprising monodisperse nanoparticles consisting of gold and possibly other precious metals or copper. Depending on the desired colors, the nature and diameters of the nanoparticles, as well as the thickness, are adjusted.