evidence: Several websites and social media posts claim that the squares you see on the bottom of your tube of toothpaste are actually part of a color code that tells you the ingredients in the toothpaste. According to the posts, green marks mean the toothpaste is made from only natural ingredients, blue marks mean it contains a mix of natural ingredients and medication, red marks means it contains both natural ingredients and chemical ingredients, and black marks means it contains only chemical ingredients. The posts warn people against toothpastes with red or black marks and encourage people to choose toothpastes with green or blue marks instead. [...] So now we know that colored marks on the end of a toothpaste tube won’t tell you what’s in your toothpaste, but there is one sure-fire way to find out for yourself. The ingredients are usually printed on the packaging, either on the tube itself or on the box it came in. The American Dental Association also notes that most toothpastes contain the same basic ingredients, like abrasives to help clean teeth, flavoring agents, humectants to soften the toothpaste, and detergents to help the toothpaste foam. The ADA also points out the importance of using a toothpaste that contains fluoride because it helps to prevent tooth decay and cavities by strengthening tooth enamel.