Nature is full of an almost infinite array of colors but some are more unique than others. Apart from the inanimate sky and water, the color blue only some animals and flowers have the privilege of possessing this color. Blue color holds different meanings in various cultures. While it is traditionally associated with sadness, blue has special symbolisms. For example, for the ancient Egyptians, blue symbolized the sky, the Nile River, creation, and divinity. For the Ute people, the color blue symbolizes the sky, water, and the sacredness of the natural world, as well as tradition and knowledge.

Here in the Rocky Mountains we hold sacred our bluebird days and while out on the trail spotting a glimpse of blue is a special treat. Some birds with blue tones fly throughout the forest. During the summer, the landscape is enriched with wildflowers that display their beauty in shades of blue, including the delicate bluebell and the blue flax. But does the color blue really exist in nature? Or is it just an optical illusion to our spectrum of vision? 

The Blue Flax flower is a perennial wildflower native to North America.

In the natural world, the colors we perceive originate in two ways: pigmentation and microscopic structures. Animals can obtain pigmentation through diet (mainly from plants), by ingesting them they extract pigments and incorporate them into their tissues such as skin, feathers or scales. Some animals, such as birds, produce their own pigments, which are reflected by light and create the different colors we see in their plumage. Animals cannot obtain a true blue color through the food they eat, as plants lack a blue pigment. Structural colors are produced by the interaction of light with microscopic structures, these structures can be photonic ridges, layers or crystals, and their arrangement and size determine how light is reflected and scattered. As light interacts with these structures, some wavelengths are strengthened while others are canceled, producing vibrant, iridescent colors, such as blue. 

The blue color that we can see in different animals is a structural color! So we could say that it is an optical illusion for our eyes. 

Some examples in nature are birds, which have an iridescent blue color in their feathers. Tiny air pockets in the feathers scatter light, creating the appearance of blue color. Some examples of birds with blue colors are the vibrant cerulean Mountain Bluebird, the deep and elegant blue Steller's Jay and the blue gray Woodhouse's Scrub Jay. 

A beautiful Mountain Bluebird caught perching fabulously on a low tree. 

One of the most popular insects is the morpho butterfly that only inhabits the tropical forests of Latin America. Its wings are distinguished by their bright blue color. There are also some blue bees, such as the blue orchard bee (Osmia lignaria) native to North America. 

Although it is rare to find blue flowers in nature, there are some such as blue bell or blue flax. These flowers contain anthocyanins, pigments that absorb red light and reflect blue light, giving them their distinctive color.

Next time you are outside remember that all colors hold their own unique story and that all may not be as it appears. The impressive variety of colors in the natural world is the result of the combination of pigment and structural colors. Sometimes we are often fooled by optical illusions or adaptations in nature such as the color blue, but just because something is not as it appears does not mean it is any less beautiful. Nature is full of this layered unseen richness and it is important to preserve all that is seen and unseen.

Ivett Lopez Garcia is a naturalist at Walking Mountains who enjoys hiking in the Rocky Mountains, enjoying the beauty of nature.