How can we see color?

Color; drawn by me

There's color everywhere: projected in the screen monitors we gaze at, in the foods we eat, and in the nature around us. But, how exactly can we see these colors? Why are objects colored the way they are? Let's find out.

How we perceive color

Imaged retrieved from LiveScience.

Light is made up of wavelengths, and each wavelength pertains to a certain color. The colors that we end up seeing are the wavelengths that are reflected back at us. 

In order to sense their wavelengths, our eyes have photoreceptors (cells that detect and respond to light) concentrated at the retina. The two types of photoreceptors are cones (activated in bright light) and rods (activated in dark conditions). These cones are the reason why we can see color! They contain photo pigments (color-detecting molecules), whereas rods only show shades of gray (Science Learning Hub). Humans only have 3 types of photo pigments: red, green, and blue (Science Learning Hub). Despite only having three cones, we can still see a whole spectrum of colors! This Ted-Ed video explains how we can perceive color despite this seeming limitation.

Interestingly, our past visual experiences with objects can also influence our perception of color — a phenomenon known as color constancy (American Academy of Ophthalmology). Even if the object is subjected to different color conditions, we will still perceive the color as the same because of color constancy. This explains why the colors remain more or less the "same" under warmer light (or even more extreme conditions) as opposed to white lights. Yet, even then, colors can still vary between us with how color is perceived individually (think back to the 2015 viral gold/white or blue/black dress)!

So, what exactly causes individual variance in sight, and what are the different forms of color vision anomalies? I'm planning to eventually write another post  that goes into depth with this topic, so let me know if there's a particular type of color blindness or condition that you'd like me to explore.

Why objects are colored

If colors are reflections of different wavelengths, then how are objects inherently colored? That's the thing, they aren't! Objects don't possess color, rather they just absorb different wavelengths, resulting in reflections that we perceive. 

Retrieved from Andres Robotics and Science.

Because white light is a mixture of all colors, white objects will look white because they reflect back all the visible wavelengths of light that shines upon them. On the other hand, colored objects reflect back only some of the wavelengths while absorbing the remaining. 

For example, if white light shines on a red apple, the apple mostly reflects back red light while greens and blue wavelengths are absorbed, resulting in us seeing red rather than other colors. However, if we look at the apple in blue light, the apple will appear dark since light is being absorbed rather than reflected!

So, what color is an object then? The answer isn't simple; rather, it really depends on what color light we are using to see the object.

If objects are colored based on wavelength reflections, then how are our digital monitors portraying various colors? I'll be writing about this next week.