Why Do We See Colors the Way We Do?

Why is the sky blue, grass green, or a ripe apple red? These may sound like simple questions, but they open the door to a much deeper mystery: how and why do we perceive color at all—and is everyone seeing the same thing?

Color starts with light, which travels in waves. Each color corresponds to a specific wavelength. Our eyes have special photoreceptor cells called cones, which are sensitive to different ranges of these wavelengths—typically short (blue), medium (green), and long (red). When light hits the retina, these cones send signals to the brain, which then translates that information into what we perceive as color.

But here’s where it gets interesting: color doesn’t exist “out there” in the world. It's not an inherent property of objects. Color is something created by the brain. An object reflects certain wavelengths of light and absorbs others. What we call “red” is just light of about 700 nanometers being interpreted by our visual system. The object itself isn’t red—the perception is happening in our minds.

So, could your “red” be someone else’s “blue”? In theory, yes. Since our experience of color is entirely subjective, there's no way to prove that we all perceive the same colors the same way. We've all agreed to call that specific wavelength "red," but what it looks like to you versus to someone else might differ entirely. This idea is known as qualia—the individual, internal experiences of perception.

It’s also worth noting that not everyone sees color the same way biologically. People with color blindness, for example, may be missing one type of cone cell, which limits their ability to distinguish certain hues. There are also tetrachromats—usually women—who may have four types of cones, allowing them to perceive a wider range of colors than most people can even imagine.

In terms of evolution, color vision likely developed as an advantage. Seeing ripe fruit, detecting predators in foliage, or noticing changes in skin tone during social interaction could all have contributed to survival. But why those particular wavelengths trigger those specific color experiences? That part is still a mystery.

Some scientists and philosophers argue that we may never fully solve the puzzle of color perception. It’s one thing to measure light and brain activity—but quite another to understand why “red feels red.”

Ultimately, color is a perfect example of how reality is filtered through biology and consciousness. What seems so obvious—like the redness of a rose—might be one of the most subjective, and unknowable, experiences we share.