When you mix two colors, red and green, what do you get?
You might have been told in art class that if you mix the three primary colors — red, yellow, and blue — you get brown. Although that is true of paint, it is not true of light. If you spin a wheel comprised of half red and half green triangular segments of color, you will observe the color yellow.
There is no yellow light there, although you observe the color yellow when the wheel is being spun — your brain is actually being tricked by your eyes. That is because your eyes are comprised of light-sensitive photoreceptor cells called “cones.” Most of us only have three cones — red, green, and blue — so there are no cones for yellow, orange, and the other colors we observe in the light spectrum. These three cones work together to show you the rest of the colors in the color spectrum, even if you aren’t actually seeing those colors with your eyes. Your brain has to compute and do the rest.
The video by Physics Girl provide you with the answer of how your eyes work, it delves into how your brain is being tricked to observe a color that you aren’t actually observing, and it is absolutely fascinating!