Another analogy might be like how a photographer burns and dodges a print in the darkroom. It is as if the brain is capable of burning and dodging on the fly. This phenomena might be further explored by looking at break lights on automobiles. Up close, there are great differences in breaklights between auto makes and models. At a distance, the lights take on a single saturated hue of red.
Variation is noticed up close, and one can pick out different textures and tones.
I will have to give this more thought. I have still not ruled out another possibility. The cones in the eye that are sensitive to red light may stimulate adjacent cells. Thus a greater intensity may generate a lighter tone of red and thus result in more variation. In film, on the other hand, I have noticed that red seems to do the opposite.