Aha! No! That link above is the standard answer that most sources give, but it is not accurate (not any more anyway). There are no separate tubes or sections inside the tube. The stripes go all the way through the tube, alongside the white stuff, a bit like a stick of rock. The reason why they don't mix up is because the coloured stripey stuff is much more sticky anf jellyish than the white stuff, so it stays separate (like a string of toffee on a blob of cream). I know all of this because I specifically bought and cut open a whole tube of toothpaste in order to do the research for a question on ABank about 2 years ago. It was one of the first answers I ever did here. Unfortunately I didn't take photos of it, so I can't show you to prove it without doing it again with another tube.