@Parsifal - colour, what a wonderful way for us humans to see the world and there are animals who can see even more, although we are one of the few species who can see colour - birds have that ability, too. But cats and dogs only see black, white and grey - however IMO they must be able to see browns and orange as well, otherwise why do these colours appear in their coats? A bull, apparently, cannot see 'red' - yet the bullfight is built around waving a red flag in front of a bull.
re men: they often have an inability to distinguish red from green.
