Why We All See Different Colors
The human eye is always processing new information. As it constantly works to send images to the brain, it can become tired. Old age, tiredness, eye strain, and genetics all affect how we see things — specifically, how we perceive color in comparison to everyone else. Furthermore, there are deeper factors, such as environment and eye biology, that significantly affect how humans process color.
Photoreceptors
The primary parts of the eye that handle color are the photoreceptors, which are divided into rods and cones. Rods absorb only dim light, while cones are able to absorb brighter light: colors. This is why, during the day, a grapefruit might look pink, but at night it looks gray: at night, natural light is too dim for the cones in your eyes to process.
Photoreceptors are known to have wavelengths at which they best perceive light. Peoples eyes naturally vary in composition and these wavelengths are different from person to person, making each eye have a slightly different ability at which they can process a certain color. Outlying circumstances, like color blindness, affect color perception as well. Essentially: its not colors that cause an issue, its the human visual system. Everyone sees the same colors, our brains just process them differently.
“For example, one person may have “red” photoreceptors, or “long-wavelength cones”, that are most sensitive to wavelengths of light around 564 nanometers. Another person may have long-wavelength cones most sensitive at 568 nanometers. This may seem like it isn’t much of a difference. However, this slight shift in photoreceptor peak sensitivity can make all the difference in the world when it comes to perceiving colors as “red” versus “orange”, or other colors (UCSB).”
Electromagnetics
All light is essentially electromagnetic radiation. The colors we see are from the visible color spectrum (a subset of the larger electromagnetic spectrum) and are made of electromagnetic waves. Electromagnetic energy is measured in Hertz (Hz), which is a unit of frequency measuring how many cycles, or waves, can be produced by a particle in one second. Wavelengths, therefore, are defined by how large they are and how fast they enter your eye. Think of it like a beach: some waves are large and don't crash onto the shore. These waves are similar to radio waves, which are roughly 3kHz-3GHz. Radio waves are the longest and lowest in frequency of those found on the electromagnetic spectrum. Other waves, like x-rays, are tiny and have a high frequency (3 x 10¹⁶-3 x 10¹⁷ Hz).
While electromagnetic energy is measured in Hz, the size of wavelengths is measured in nanometers. Since colors are dependent on the size of a wave, and not its frequency, colors are measured in nanometers (nm).
Electromagnetic waves come from charged particles. These particles produce energy that creates an electric field. Particles release energy through motion. This movement is done in an oscillating, or back and forth, motion. These oscillations create ripples within the electric field and produce a magnetic field. Wavelengths are produced from oscillating motion, and are measured from peak to peak in nanometers. Nanometers are incredibly tiny — 1 billionth of a meter — and each of the traditional colors we see — red, orange, yellow, green, blue, indigo, and violet — all exist within this incredibly small range of nanometers. Given that nanometers are so small, the color that travels on one wavelength is incredibly different than the color that travels just a few nanometers away from it.
Lighting and Context
When you look at an object, you don't just see what it is, but you also take in the environment around it. This high level of stimuli makes it harder for our brains to perceive colors, so the brain uses a filtering process that helps it recognize colors faster.
One of these filters is the surrounding light conditions. Depending on the lighting, the time of day, and how bright or dark objects around the one you’re looking at are, the colors you see will be different. For example: objects often appear red at dawn and dusk, but blue in the middle of the day.
This plays into a phenomenon called color constancy. Color constancy is the psychological theory that humans have the ability to perceive the color of an object invariable of the color of a light source. Color constancy states that humans, who see a blue object for example, still see the object as blue when the light around it changes. Even if the sun is setting and the blue object looks violet, the human visual system unconsciously recognizes that this is the same color it saw before — that the color itself has not changed, just its context.
When combined with the unrecognizable but drastic differences between individuals eyes, it is clear that there is a color discrepancy between humans — one largely caused by biology and external environments.
