Sinnott-Armstrong, postdoctoral researcher of ecology and evolutionary biology at CU Boulder, quickly asked if she could take a specimen back to the lab. She wanted to know: What made these berries so blue?

Sinnott-Armstrong's results are now published in the journal New Phytologist. The study confirms Lantana strigocamara as the second-ever documented case of a plant creating blue-colored fruits with layered fat molecules. She and her co-authors published the first-ever documented case, in Viburnum tinus, in 2020.

The two plants are among only six in the world known to make their fruits' hues using a trick of the light known as structural color. But Sinnott-Armstrong has a hunch there are more.

"We're literally finding these things in our backyards and on our streets, people just haven't been looking for structurally colored plants," said Miranda Sinnott-Armstrong, lead author on the new study. "And yet, just walking on Pearl Street, you're like, 'Oh, there's one!'"

Structural color is very common in animals. It's what gives peacocks' otherwise brown feathers their brilliant greens, and many butterflies their bright blues. But this optical illusion of sorts is much rarer in plants, according to Sinnott-Armstrong.