While violet hits your eye with a specific wavelength, purple only exists in your perception — a clever construct built from conflicting input.

So, when looking at the green part of the illusion, it is the green and blue cones that get fatigued and fail to respond properly when the white screen flashes up. But the red cones that were not ...

Picture red and blue light—two bookends of the spectrum—making it to your eyes simultaneously. These wavelengths are quite distant, with green and ... of what this optical illusion is about ...