I distinctly remember this eighth grade grammar lesson, because my teacher marked me wrong for not putting a comma in “red, pickup truck” even though the rule she taught us says there shouldn’t be one. the rule supposedly is that you should put in a comma, if the comma could be replaced with “and,” e.g. “the big, round, gray rock” could be “the big and round and gray rock.” so tell me Mrs. B, who the hell is out here saying “the red and pickup truck”? who would say “the truck is red and pickup”?