From the mid 1970s to the mid '80s, red M&M's disappeared. American consumers had become worried about the safety of red food coloring after some questionable Russian studies prompted the FDA to look into whether one particular dye might be causing cancer in rats. But years later, the red M&M made a triumphant return, thanks in part to a college kid in Tennessee and an inside joke that took on a life of its own. Produced by Sarah Wyman, with Charlie Herman and Julia Press.See the rest of the story at Business InsiderNOW WATCH: Why thoroughbred horse semen is the world's most expensive liquidSee Also:31.