When you see a peacock with brilliant green in its feathers, realize that it has no green feathers. Its feathers are actually brown, but God has used a clever optical trick to make them look green to us. We call it structural color. Likewise, many butterflies have bright blue spots on their wings, but there are no blue pigments in a butterfly’s wings.
Some plants produce fruits that look blue to us without having any blue pigment in the fruits. The only plants known to produce blue fruits in this way are Viburnum tinus and Lantana strigocamara. You will not get a blue stain if you crush their berries in your fingers. On the other hand, if you crush a common blueberry, its blue pigments will stain your fingers.
When you see a blue pigment, it is blue because it absorbs all other colors while reflecting blue. Structural color uses microscopic pyramid-like structures that manipulate the light. Since blue light has higher energy than other colors, it escapes the structure. Structural color requires no pigments, and you might call it an optical illusion.
Color is essential in the natural world. For example, animals with color vision use colors to camouflage, attract others, or discern whether something is good to eat. The problem with using pigments to produce color is that the chemistry to get a particular color is quite complex, but structural color does not involve any chemistry.
People have used chemicals to produce the colors we see in our fabrics, but some colors can be costly and time-consuming to produce. God has created a chemical-free method to produce much of the beauty we see in the world around us. Beauty in structural color gives evidence of a wise Creator.
— John N. Clayton © 2022
Reference: National Science Foundation Research News