I'm not sure what I will say now, but it seems like if there is a red square on the spine, then there are more "chemical" elements in the toothpaste. And if black is more "natural". Someone told me this long ago. But since then I draw your attention to the fact that on pastes with herbs and propolis they are really black. And the rest are red. There may be exceptions
This is the cut mark for the machine, which seals and cuts the filled finished tubes from the base. The photocell catches this mark, and the machine cuts it off with a knife.