This idea that creatures from outer space are green might have begun in 1809 with a satire by Washington Irving. Irving’s Lunatics and Edgar Rice Burroughs’ green men of Mars, have never been seen, so we cannot verify that they are green. If they eventually arrive and say “Take me to your leader,” it probably won’t matter what color they are. Appropriately, most of us reference “little green men” more in jest than in earnest.