The colored squares or rectangles found at the crimped end of toothpaste tubes are the subject of a persistent urban legend. This myth claims the colors indicate the composition of the toothpaste, with each color supposedly corresponding to different ingredients: black for all chemical, red for chemical and natural, blue for natural and medicinal, and green for all natural. This interpretation is demonstrably false and lacks any basis in scientific or manufacturing reality.
The marks serve a purely functional purpose in the manufacturing process. These rectangles, often referred to as “eye marks” or “color marks,” are read by optical sensors during the filling, cutting, and sealing of the toothpaste tubes. The sensors detect the contrast between the mark and the tube’s background, ensuring the machinery cuts and seals the tube at the correct position. This automated process relies on consistent visual cues to maintain efficiency and accuracy in high-speed production lines. The color of the mark is chosen to provide maximum contrast with the tube’s design, ensuring reliable detection by the optical sensors.
