However, we do not perceive blue as less vivid than green or yellow or red all colors appear psychologically comparable. Somehow we need to amplify the input from the S cones. The slides presented are how the neural coding in the eye would look for each of the opponent process receptive fields. Blue represents short wavelength cones, green represents medium wavelength cones, and red represents long wavelength cones. Black represents the ganglion cell.
Color is processed using input from multiple ganglion cells.
Remember this is similar to the cones. The cones code color based on the input from all 3 cones. If the short wavelength cones fire a lot and the medium fires less than that, and the long fires even less than that, your eye is coding that you are seeing the color blue. If the medium and the long wavelength cones fire about the same amount, but the short doesn t fire very much, chances are you are seeing green-yellow. This system works in the same way.