What visual phenomenon does an individual experience when they cannot see one color while seeing its opponent?

The visual phenomenon described, where an individual cannot see one color while perceiving its opponent, is most accurately identified as opponent processing. This concept is rooted in the opponent process theory of color vision, which suggests that the human visual system interprets colors in terms of opposing pairs. Specifically, colors are grouped as red versus green, blue versus yellow, and black versus white. When one color is stimulated, the perception of its opponent is suppressed, meaning that if you are viewing red, for instance, green perception becomes temporarily less active or even absent.

In this system, the brain processes sensory input from the cones in the retina in such a way that it enhances contrast and contributes to our ability to see a wide range of colors. This mechanism is crucial for distinguishing colors in various contexts and is especially relevant when one color dominates the visual field. While other concepts such as color constancy, color blending, and simultaneous contrast relate to aspects of color perception, opponent processing specifically addresses the suppression of one color in favor of its rival when both colors are present.