That's fascinating, I didn't know that. I wonder if we're so good at seeing greens because so much of what we can eat and not eat is green. Those ancestors who were good at telling the difference, and identifying ripe stuff might have had an advantage.You can also see that there are a lot more 'greens' than any other color - we're most sensitive to green light. (The diagram is, roughly 'perceptually uniform', meaning that the same distance anywhere the diagram corresponds the the same percieved amount of difference in color. It's not quite apparent though since, again, your monitor doesn't actually reproduce the entire thing).