In our industrialized world, blue is one of the most common colours, lining our clothes, cars, and furniture. However, this was not always the case. 20,000 years ago, cave paintings did not depict the use of blue dye. The ancient Greeks only used vague descriptors to describe blue objects like the colour of the sea. Only 6,000 years ago were the Egyptians able to synthesize the first blue pigment through the use of lapis lazuli, a rare stone. The world blue also came from the Egyptians. Nowadays, most cheap blue dyes used for painting and dyeing are synthetic blues. The production of these blues uses commercially made minerals that mimic natural blue reservoirs like ultramarine.
What colour are blue jays?
Many brightly coloured birds such as the cardinal produce a brightly coloured pigment, but the feathers that blue jays have contain a brown pigment called melanin. However, our eyes perceive the feathers of the Blue Jay to be blue due to a phenomenon called light scattering.
Light scattering occurs when light hits a surface. Usually, all the light is reflected back, but, in the case of the blue jay’s feathers, only blue light is reflected back. This is because the feathers have tiny air-pockets on them which trap all wavelengths other than blue. In result, only blue light reflects back, giving the illusion of blue.
The difference between making a blue pigment and trapping wavelengths is that a blue pigment absorbs and reflects wavelengths while trapping wavelengths, like how most animals that appear blue work, prevents wavelengths from being reflected. This means that if you were to disrupt the air-pockets on a blue jay’s feather, the feather would turn brown due to the pigment melanin. The air bubbles would be unable to prevent wavelengths from being reflected.
Only 1 percent of animals that look blue make blue
With all this being said, what animal is actually blue? Out of all the species of butterflies that appear blue, only Nessaea Obrina butterflies actually produce a true blue pigment. The reason that animals resort to faking a blue pigment is that they can’t get the dye from their food. Many animals like flamingos get their dye from what they eat, but most primary producers like plants don’t produce blue dyes. Most plants don’t produce blue dye because blue light has a high amount of energy. By reflecting blue light and appearing blue, plants would be relegating themselves to lower energy yields. On a side note, a plant that produces a blue dye is the commelina benghalensis. The often perceived weed found in India and China uses several pigments to produce a blue coloured pigment.
Animals, therefore, would need to synthesize blue dye if they wanted to produce a blue colour and this would be less efficient then faking a blue colour.
One other intriguing part about the research was why appearing blue was beneficial for prey? Blue is a powerful colour in nature because it is a warning sign to predators that the animal is poisonous. Smaller prey try to capitalize on the warning effects of blue by imitating it.
The colour blue has always intrigued me as being rare. I learned how hard it was to produce blue when I read the book “Gathering Blue” by Lois Lowry. Kira, the protagonist, hopes to create a blue dye to aid her in embroidery and this goal leads to several revelationary events for her. The colour blue just appears so much in modern day to day life that learning the rarity of the colour in nature is hard.