Seeing a greenish-red, or any "impossible color," is a trick of the eye, leveraging the opponent-process theory of color vision. Our eyes don't actually perceive these combinations directly; instead, we can create the illusion through sensory adaptation.
Understanding Opponent-Process Theory
Our perception of color isn't based on simply detecting red, green, and blue light independently. Instead, our visual system processes colors in opposing pairs: red vs. green and blue vs. yellow. Staring at one color for an extended period fatigues the corresponding receptors. When you then look at a white or neutral background, the opposing color is perceived as an afterimage.
How to Create the Illusion of Greenish Red
- Find Strongly Saturated Colors: Locate a highly saturated red object and a highly saturated green object. The intensity of the colors is crucial for success.
- Adapt to Red: Stare intently at the red object for at least 30 seconds. The longer you stare, the stronger the effect will be. Try to focus on a single point within the red area to avoid eye strain.
- Shift to Green: Quickly switch your gaze to the green object. You should see a ghostly reddish tint overlaying the green. This is because the red receptors in your eyes are fatigued and less responsive, allowing the green to dominate but still showing a trace of the prior red stimulation.
Important Considerations:
- Individual Variation: The strength of the afterimage and the ease of seeing the "impossible" color will vary among individuals.
- Color Saturation: Using deeply saturated colors is essential. Pale or dull colors will likely yield weaker or nonexistent results.
- Eye Strain: Avoid prolonged staring to prevent eye strain. Take breaks if needed.
Why Some People May Not See it: Color Blindness
As mentioned in the provided Reddit thread, individuals with red-green color blindness may not be able to experience this illusion as readily, or perhaps at all. Their color perception is already different, impacting their ability to distinguish between these colors and perceive afterimages in this way. The differences in how people perceive colors are a significant aspect of this phenomenon.
Conclusion
This method relies on fatiguing color receptors in the eye to create an illusion of an "impossible" color. The result is a perceptual trick, not a physically existing color combination.
