ELI5: How do our eyes see color?

Context: Science 5 views Feb 23, 2026 2 min read

Imagine the world is made of light! Light travels in waves, like waves in the ocean.

  • The sun (or a lamp) sends out white light, which is actually all the colors mixed together!
Think of your eyes as having tiny doors called cones. We have three main types of cone doors:
  • One that likes red light waves.
  • One that likes green light waves.
  • One that likes blue light waves.
When light bounces off an apple, the apple's surface absorbs most of the colors, but it reflects the red light waves.
  1. The red light waves enter your eye.
  2. They bump into the red cones.
  3. The red cones send a message to your brain.
  4. Your brain says, "Hey! I'm getting a lot of red signal!"
  5. So, you see the apple as red!
If something is blue, it reflects blue light waves, which trigger the blue cones. If it's green, it reflects green light waves, which trigger the green cones.

What about colors like purple? Purple light is a mix of red and blue light waves. So, both the red and blue cones send messages to your brain, and your brain mixes the signals to show you purple!

If all the cones are activated equally, you see white! If none of the cones are activated, you see black!

People who are colorblind might be missing one or more types of cones, or their cones might not work properly. That makes it harder for them to tell certain colors apart.

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