Puffin beaks are fluorescent Humans see colours that are a mix of red, blue and green light, he notes, while birds have a fourth colour in the mix — a property called tetrachromatic vision.Unlike humans, birds have always known about the extra colours in the puffin bill. That's because they can see a whole other dimension of hues, said Dunning.
But, alas, this color space has some unhelpful properties. For one, not all triplet values (also called tristimulus values) are physically possible. Consider the LMS coordinates (0, 1, 0). To physically achieve this coordinate, we would need to find some way of stimulating the M cones without stimulating the L or S cones at all. Because the M cone’s sensitivity curve significantly overlaps at least one of L or S at all wavelengths, this is impossible!