Perception of color of an object or medium with our eyes depends on the interaction of the light and that object. Reflection, transmission, absorption, scattering and diffraction are preliminary optical phenomena which occur when light (visible) interact with an object. In many cases, the absorption of the incident light by the medium is dominant however reflection, diffraction and scattering are the main cause of the color that our eyes receive from surrounding. That means manipulation of the light matter interaction by engineering of the outer surface induce different color. This is indeed the basics of structural color base on metasurface (or metamaterials). It is already known that metamaterials optical properties can be tuned by changing the geometry and arrangement of their building block. So, it is possible to adjust the amount of the color that reach to our eyes by manipulation of the structure in metasurfaces and hence make new color.
This is generally done by altering the size of the components of the metasurfaces, re-arrangement of the surface patterns as well as changing the material constituents of the metasurface. For instance, if silver metallic double-cylinder of certain size atop of silver mirror leads in green color, enlarging the size of the features (building block) can result in blue color (see the following illustration. This is because the reflection of the light in former case is peaked at green part of spectrum (shorter wavelengths are absorbed due to plasmon resonance) while the blue wavelengths are completely reflected in latter case. The concept of metasurface structural color is nowadays attracts the attention of scientists around the world because it could enable printing in smaller scale and above all it free designers from using of toxic colorant pigments.