How do we see colors in our vision?
Different kinds of light are always interacting with your eyes. You see color when light reflects off an object, enters your eyes, then gets processed by your brain. But these steps aren't as simple as they seem.
The color-sensing cells inside your eyes
You have a thin layer of cells in the back of each eye called a retina. This includes millions of photoreceptor cells that react to different kinds of light.
There are two types of photoreceptors: rods and cones.
Rods help you see in low light and around your central field of view (your peripheral vision). They don't help you see in color, only in black and white.
Cones are the part of the eye that lets you see colors. They also help you make out fine details and see in bright light.
You have millions of color-sensitive cone cells in the back of each eye.
The average human has about six million color-receiving cones in their eyes. That might sound like a lot, but not compared to your rod cells. You have more than 100 million of those.
Someone with normal color vision has three types of cones. Each one responds to a different color:
Red
Blue
Green
When colored light enters your eye, it "activates" the color receptors that go with that color.
Colors like yellow, purple and brown are a blend of these colors, so they activate two or even all three types of cones at once. When all three cones react equally, you see the color white. Researchers have also found that some cones only respond to white.
Take this daytime flower scene as an example.
The vibrant petals absorb most of the sunlight but reflect the red light away. Some of this reflected light travels into your eye and activates the red cones in your retina.
Elsewhere in the scene:
The flower and background in this scene activate all three types of cones at the same time.
Light from the leaves and trees is activating your green cones.
Light from the sky is activating your blue cones.
Light from the pollen in the center of the flower is activating your red and green cones at the same time. That makes it look yellow.
In an instant, these color signals leave your eye through the optic nerve and make their way toward your brain.
