How Do We See Red? Count the Ways

In fact, human eyes, like those of other great apes, seem to be all-around fabulous fruit-finding devices, for they are more richly endowed with the two cone types set to red and yellow wavelengths than with those sensitive to short, blue-tinged light. That cone apportionment allows us to discriminate among subtle differences in fruit ruddiness and hence readiness, and may also explain why I have at least 40 lipsticks that I never wear compared with only three blue eye shadows.