The red smoke of a flare on a roadway warns motorists to be cautious, but the anthraquinone dyes currently used to produce this smoke are thought to be harmful to human health. Now, researchers reporting in ACS Sustainable Chemistry & Engineering have identified a less toxic, "greener" alternative—an organic dye called pigment red 254 (PR254). It also forms a red-colored smoke cloud more effectively than current dyes, the researchers say.