Scientists have long known the molecular mechanisms that give a plant called a dahlia its wide spectrum of color. These colors are created by the accumulation of flavonoids, with the over 20,000 varieties of dahlia cultivars ranging from white to purple. But the black dahlia is rare in comparison to the other colors. In 2012, scientists uncovered the reason: the black cultivars had a low concentration of flavones; this, in turn, favors the accumulation of the anthocyanins—and the dark color is formed.

A pigment called bilirubin, found in animals, was only recently found in plants. For example, in humans, bilirubin is responsible for the yellow color we see in people who have jaundice (as a result most often of poor liver function). It is formed when the pigment hemoglobin, which makes our blood red, breaks down into heme; that further breaks down from heme into bilirubin. Recently, bilirubin has been found in the orange fuzz on seeds of the white Bird of Paradise—but in this case, it’s not hemoglobin breaking down, but chlorophyll molecules. Apparently, the chlorophyll has the same structures as heme— and after breaking down into another molecule, it eventually results in bilirubin.