Animals come in all sorts of colors, and while the animal kingdom has most of the rainbow’s colors at its disposal, there are a few exceptions. Some animals, for example, may appear blue at first glance, but most of these animals are tricking your eyes with light.
An animal’s color typically comes from pigment, which often takes the form of pink, orange, or even green to name a few, but pigments are almost never blue. The blue morpho butterfly, for instance, appears blue, but it only looks this way because of how microscopic structures in its wings interact with light. This is comparable to how passing light through a spectrum scatters visible color.
We know this because looking at the blue morpho butterfly from different angles reveals other colors besides blue, almost as if the wing was iridescent. Wetting with alcohol further disrupts this light-based color scatter, making it appear green until the alcohol dries. The blue morpho butterfly isn’t the only example of this either; other animals appearing blue use similar tactics to deceive our eyes, including birds and fish.
But while the vast majority of ‘blue’ animals aren’t truly blue, there are some exceptions. Less than 1% of the animal kingdom is thought to have any true blue pigment. Some examples of this small percentage are the olive wing butterfly, which sports true blue pigments in its wings, and the blue poison dart frog, which has blue pigments throughout its body.
No one really knows why the color blue is so elusive in the animal kingdom, but scientists hope to answer that question as research into the matter continues.