Just learned the correct term for the a cone or rod is hit by a photon of light - it is isomerized. Cone are sensitive to different ranges of the electromagnetic spectrum, but they have no clue as to the wavelength that triggered an event. Cones are color blind.

It is how the event is processed makes a difference. A quantum packet of photons could cause events from long & medium wavelength cones, but not short wavelength cones. The pairing of cones is the critical second stage - Herrings Opponent theory. This is still part of retinal.

Without getting into cortical processing. Every color blindness simulation model has problems. Even though Meyer- Greenberg provides the best simulation, it is based on CIE xyY. I modified their formula to account for different Illuminants, but it still falls short.

Brettel-Vienot-Mollon is essentially a Chromatic Adaptation Transform that only modifies cone responses as do all CATs. Machado-Oliveria-Fernandes is also a CAT, but throws in the opponent theory. All present problems when working with Color Appearance Models (CAMs).

Every CAM first applies a transform for cone rsponse and then an opponent theory transform. Technically, a CAM should be the color space for color blindness simulation. For image processing an Image Appearance Model (IAM) is needed.