I found this a fascinating, and quite interesting, video about biological blue in nature, from butterflies to eyes, and why it is so very rare. And beautiful!

Among living things, the color blue is oddly rare. Blue rocks, blue sky, blue water, sure. But blue animals? They are few and far between. And the ones that do make blue? They make it in some very strange and special ways compared to other colors. In this video, we’ll look at some very cool butterflies to help us learn how living things make blue, and why this beautiful hue is so rare in nature.