My favorite one, similar to this, is impossible colors. https://sciencenotes.org/impossible-colors-work-see/ https://sciencenotes.org/impossible-colors-work-se

My favorite one, similar to this, is impossible colors. https://sciencenotes.org/impossible-colors-work-see/ https://sciencenotes.org/impossible-colors-work-see/ By training your eye on a vivid color, then withdrawing the stimulus, and presenting an opposite or complementary color, you can experience physically impossible colors, like blue-yellow or red-green.