Why does a red light say stop and a green light say go? What primeval protocol is being followed here? Wouldn't a ripe red fruit say 'pick me now?' Wouldn't a bright green tree in your path say 'Stop and figure out a way to get round this.' Philosophical conversations like this are best held when neither participant is in charge of a moving vehicle! Right now, you're seeing signs and symbols which have a fairly clear meaning. The time to wonder what else they could imply is once you've heeded the obvious!