evidence: That colored block on each tube of toothpaste has generated all kinds of myths. Here's the real explanation! [...] What about the colorful blocks at the end of a tube of toothpaste? There’s a reason those squares exist! And no, it doesn’t have to do with ingredients. [...] Many people believe the color blocks denote the kinds of ingredients in each tube of toothpaste. We also see this kind of thinking when it comes to colors on the bottom of potato chip bags.