evidence: Is there a secret color code hidden on the ends of toothpaste tubes that tells you if it the toothpase contains chemicals or other ingredients? No, that's not true: the colored squares or rectangles on toothpaste tubes are just a marking that is used by the machines used to fill toothpaste tubes, it has no relation to the composition or ingredients of the toothpaste. [...] What Does the Toothpaste Color Code Mean? | Colgate® Oral Care [...] The reason for the marks has to do with how toothpaste tubes are made. The marks help light sensors detect the end of the tube, so that the machines used to prepare the tubes knows where to cut or seal them.