We don't see color

The names used to describe CVD (Color Vision Deficiency) confuse, but do not clarify, the functioning of the cones. There are no red cones, green cones or blue cones. RGB is a merely a human convention for describing colors by adding red, green and blue. Great for defining light sources, but not for understanding color vision.

Object colors are based on CMY (Cyan, Magenta and Yellow). The mind warping aspect of objects is understanding the difference between refraction and reflection. Forget reflection. Think refraction. The molecules in any object absorb the photons of light. Absorbing energy results in the release of energy. The release of energy is a different frequency. This is refraction. It is a subtractive process. This is why paints use CMY for mixing colors.

Vision research groups cones into three categories according to their sensitivity to different wavelengths of light. Again, we are talking about energy. The resulting wavelength graph for the different cones are as follows:

The cones that have a peak abundance of 559 nm are known as the long wavelength cones. The medium wavelength cones are those whose peak abundance centers on 531 nm. The short wavelength cones have a much higher center wavelength at 419 nm. The acronym is LMS. Many explanations refer to long wavelength cones as red, medium wavelength as green, and short wavelength as blue. The reality is that a person can have 100% protanopia (no long wavelength cones) and still visualize some shades of red. The medium wavelength still respond to shorter wavelengths of the color red.

The Quick Test feature of my Color Simulator apps provides a good demonstration of the overlapping of the wavelength response curves. Just follow color code values, as you adjust the sliders. Even a person with protanopia has some red response. Change the type to deuteranopia, and notice the similarities and differences.

Cones respond to a range of wavelengths of light. The terms red, green, and blue tend hide this phenomenon. The cones of the eye do not see color, they are receptor cells that respond to light energy of different wavelengths. The vision centers of the brain create the vision of color based on the information received from the cones.

The overlap of the long and medium wavelength curves leads to the term red-green color blindness. This is wrong. There are differences between protanopia and deuteranopia, as they represent the loss of different cones.