evidence: According to several websites and social media posts, the claim is that the little squares you see on the bottom of a tube of a toothpaste are some sort of toothpaste colour code, revealing the nature of the materials within. The post claims that a green mark means the toothpaste is all natural, a blue mark means it contains a mix of natural ingredients and medicine, a red mark means it contains natural ingredients and chemical ingredients, and a black mark means it contains all chemical ingredients. The posts warn people away from using toothpastes with black or red marks and encourage people to pick toothpastes with green or blue ones. [...] The bigger issue with the colour code hoax is that it's not accurate information. Companies don't mark their toothpaste tubes with little coloured squares in an attempt to pull the wool over consumers' eyes. In fact, as Snopes points out, 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. [...] If a blue or green box on the end of a toothpaste tube isn't going to reveal its contents, how can you know what you're about to brush your teeth with? Fortunately, there are easy ways to find out the ingredients in toothpaste. The information is usually printed on the packaging, either on the tube itself or on the box it came in.