Rod and cone cells are at the top. Optic nerve fibers leading to the brain may be seen at bottom right. Normal humans have three different types of cones with photo-pigments that sense three different portions of the spectrum. Light at any wavelength in the visual spectrum range from 400 to 700 nm will excite one or more of these three types of sensors. Our mind determines the color by comparing the the different types of cones sense.
Individual cones signal the rate at which they absorb photons, without regard to photon wavelengths.
Though photons of different wavelengths have different probability of absorption, the wavelength does not change the neural effect that it has once it has been absorbed. Thus, single photoreceptors transmit no information about the wavelengths of the photons that they absorb. Our ability to perceive color depends upon comparisons of the outputs of the three cone types, each with different spectral sensitivity. These comparisons are done by the neural circuitry of the retina. These are currently the best charted visual areas, but not the only ones.