English: Seeing red. A. Light from the sun hits the apple. Some wavelengths are blocked by the chemicals in the apple’s skin. B. Reflected wavelengths pass through the pupil and excite the cone cells at the back of the eye. C. The cones send a coded message to the brain about the wavelengths entering the eye. In this example, the L-cones are very excited, the M-cones are a little bit excited and the S cones are hardly excited at all. The brain translates this code into a sensation of “red”.