The rarest color is at the end of the rainbow. The physics of light and evolution explain everything.
Green, as we well know, is everywhere in the natural environment of our planet, but there are colors that we hardly see.
An example that may immediately come to mind is the azul. In addition to the vast sky, there are few flowers, birds and amphibians that ‘rock’ the color (which is not the color) of the sea. But from a scientific point of view, there is an even rarer color in nature.
The explanation lies in the physics of light and evolution. The colors we see result from the way matter interacts with light, more specifically, which wavelengths are absorbed or reflected. Red light corresponds to longer, less energetic wavelengths; blue and violet, at shorter and much more energetic wavelengths.
Green is common because it is at the heart of the mechanism that sustains almost all life on Earth: photosynthesis. Plants use the pigment chlorophyll, which absorbs mainly red and some blue light, reflecting green light, which is why leaves appear that color to us. This combination is energy efficient at exciting chlorophyll’s electrons and converting light energy into chemical energy, explains .
When we go into the blue, things get complicated. Blue light is so energetic that most pigments tend to absorb it rather than reflect it. Biochemically, “giving back” blue is difficult; it is more difficult to absorb this energy.
Therefore, many of the blues we see in tropical birds, butterflies or beetles do not come from true pigments, but from microscopic structures that scatter light and create the illusion of blue, a phenomenon known as structural coloration. Producing and maintaining these structures is complex and energetically demanding, which helps explain why so few organisms develop them.
But if blue is difficult, with violetthe difficulty goes up another notch. It is further located at the energetic end of the visible spectrum. Everything that makes blue rare applies even more intensely to violet: it is extremely difficult to create pigments that reflect it and it is technically demanding to build microscopic structures capable of generating this tone through structural coloration.
Result? Violet is practically non-existent in the living world.
