My good friend, Professor Tom Skalak from the University of Virginia sent me a link to an article by researchers at Cambridge investigating a type of African berry called Pollia. Here is how phys.org summarized the find:

The ‘brightest’ thing in nature, the Pollia condensata fruit, does not get its blue colour from pigment but instead uses structural colour – a method of reflecting light of particular wavelengths – new research reveals. The study was published today in the journal of the Proceedings of the National Academy of Sciences.

In The Rarest Blue, we discuss in great detail the five ways that nature “makes” blue. Examples of the first four correspond to (1) the color of the sky, (2) of peacock’s feathers, (3) of the ocean, and (4) of gems (such as lapis lazuli). Blue that comes from white light bouncing off a pattern of suitably spaced reflectors, known as structural color generation, is way number two. The blue of a bluebird or Morpho butterfly – and, it turns out, of these Pollia berries, is created in that way and typically leads to a very bright, striking blue.

The fifth way is that of color created by pigments – and that accounts for virtually all of the color that we see in the objects around us. Pigments are molecules or atoms that absorb light of certain wavelengths and our eyes perceive the complementary color on the color wheel. In order to generate blue using pigments, red-orange light would have to be absorbed. This, however, is not a trivial matter. In fact, in all of nature, there is only one organically manufactured molecule that can accomplish this feat …

Another few weeks till the book comes out. I don’t want to give away the surprise ending!

The full article in PNAS on the Pollia berries can be found at this link.