When we talk about mixing colors, it’s often because we’re mixing paint, but what about light? The retinas in our eyes respond to light differently because of two types of photoreceptors: rods and cones. Rod cells help us with night vision, motion detection, and peripheral vision. Cone cells come in three types — red light, blue light, and green light — and they not only help us to see red, blue, and green, but they work together to see all colors.

They’re also why you see the color blue after you’ve been staring at yellow for a long time… or green after looking at pink. Cone fatigue.

Above, Physics Girl‘s Dianna Cowern explains how your eyes perceive color.

Related illusions: 12 fascinating optical illusions show how color can trick the eye, and Spooky Science: Discovering the Eerie Colors behind Afterimages.