Part of the show Science of Sight, Eye Diseases and Animal Vision
Graham in Norwich asked:
Why are the cones in our eyes red, green and blue? Why not red, yellow and blue? How can we see yellow?
They're not actually red, green and blue at all, although that's what we tend to call them. They're actually blue, green and yellow. The long wavelength cone absorbs mainly in the yellow and not in the red, so that's how we can see yellow.