fungus

There's a type of mustard plant, called "Holboell's rockcress" which naturally grows a dainty, light blue flower atop its narrow stem. Sometimes you'll see a Holboell's rockcress sporting a bright yellow cluster of leaves that looks suspiciously like a buttercup.

If you visit an archive with scrolls, illuminated manuscripts, or old books on display, you might notice a particular kind of round, yellowish, or orange-tinted stain on some of the paper artifacts. This color effect is called foxing, and paper so affected is said to be “foxed.”

If I asked you what lichen was, you might say that it's a symbiotic organism that's made up of fungus joined with algae or cyanobacteria. This is what scientists would have said from 1867 up until recently.