Here are all the colors that iNaturalist uses and what they generally mean:
Green = Plants
Red = Insects, Molluscs, Arachnids,
Blue = Ray finned fishes, Birds, Amphibians, Reptiles, Mammals, and “Other Animals”
Pink (kind of a Magenta) = Fungi Including Lichens
Brown Red = Kelp, Diatoms, and Allies
Purple = Protozoans
Gray = Unknown, Prokaryotes, Bacteria, and Viruses (see discussion of the problems with this grey icon here: https://forum.inaturalist.org/t/icon-color-for-prokaryota/1464)
Apheloria virginiensis would fall under the “Other Animals”, which includes an assortment of organisms like Myriapods, Cartilaginous fish, Crustaceans, Flatworms and Worms, Sea Stars, Rotifers, etc.