I’m seven years old, and I’m standing in front of an unopened packet of new toothbrushes: four, one for each member of my family. And I know I have a big choice in front of me, because the colour of the one I choose will dictate the safety of all of them. Red? No, too close to blood, which is murder, which is death. Green? A shorthand for sickness, which is death. Blue? Water, which could be drowning, which is death. I settle for yellow, even though it could represent the sun swelling to destroy the whole planet, but that seems like the least likely potential death scenario so, reluctantly, I brush my teeth with that one. I know, somewhere inside me, that this is a lot of worry to be applying to a toothbrush, but I’m not risking disaster for some foolish green-toothbrushed hubris.