First 3D views explain how primate cone pigments distinguish red from green

Human color vision depends on three types of cone cells in the retina.

Although all three contain the same light-absorbing molecule, 11-cis-retinal, differences in the surrounding protein determine sensitivity to red, green or blue light.

Understanding how these subtle protein differences produce such precise color discrimination has been difficult because cone pigments are highly unstable and structurally challenging to study. ...