Imagine you're looking at wall with 3 colored circles, red green blue - something happens and you can now see a fourth circle that wasn't there before. You've

Imagine you're looking at wall with 3 colored circles, red green blue - something happens and you can now see a fourth circle that wasn't there before. You've experienced it already... by shining a black light on ultraviolet pigment. It's the same principle behind color blind test patterns: https://cdna.allaboutvision.com/i/eye-exam-2017/color-blind-red-green-330x330@3x.png https://cdna.allaboutvision.com/i/eye-exam-2017/color-blind-... A color blind person sees one color - a normal vision person sees two.