Why Does the Same Color Look Different Under Different Lights?

Imagine you have a bright red apple. If you hold it in your kitchen under white lights, it looks red. If you take it outside at sunset, the sun is orange, so everything looks orangeish, but that apple still looks pretty red to you! This trick is called color constancy.

Your eyes see two things: what color an object actually is and the color of the light hitting it. Your brain does a quick math problem. It checks the light source (like the sun or a lamp) and subtracts that color from what you see.

If the apple is hit by orange sunset light, your brain says, "Okay, the light is orange, so I will remove some of that orange." This leaves just the red part. Without this trick, the world would look like it was wearing colored glasses that changed every time you moved.

Artists use this when painting. If they paint a blue shirt in sunlight and indoor lamp light, they must make sure the audience still sees it as blue in both places. Your brain works hard to keep colors stable so you know exactly what you are looking at.