The theory is that:
The tiny symbol, on the sealed end of the tube, comes in green, blue, red or black.
Green: If the code is green then it means that the toothpaste contains only natural ingredients.
Blue: Blue color means the toothpaste’s composition is natural in combination with medicines.
Red: If the code is red then the toothpaste contains natural substances and chemicals.
Black: If on the bottom of the tube is found black code it means that the paste contains only chemicals.