AUDIE CORNISH, HOST:
Currently, we are nerding out on color in a series that will hopefully inspire you to look at the world hews a little differently. Color is everywhere. But we don't often stop to think about how color affects us and the role it plays in our lives. NPR's Nell Greenfieldboyce set out to define color. The answers from scientists may surprise you, but she started with a budding expert.
NELL GREENFIELDBOYCE, BYLINE: A ritual of childhood is learning to name the colors. At first, kids have no clue. Often, they'll just say everything is boo. Then, they start to catch on. Here's one kid from my neighborhood.
What color is this fireman hat?
UNIDENTIFIED CHILD: Red.
GREENFIELDBOYCE: A red fireman hat.
What color is this construction worker hat?
UNIDENTIFIED CHILD: Is it orange? Is it white? Is it blue? Is it yellow?
GREENFIELDBOYCE: Looks yellow to me.
But learning the colors doesn't mean you have any idea what color actually is. Mark Fairchild is a scientist who studies color at the Rochester Institute of Technology. It drives him nuts when his physicist friends define color as just a wavelength of light.
MARK FAIRCHILD: My usual quick answer to that is - I can take any wavelength and make it appear almost any color.
GREENFIELDBOYCE: That's because color is not something out there in the world separate from us.
FAIRCHILD: The agreed-upon technical definition of color is that it's a visual perception.
GREENFIELDBOYCE: You might say, for example, this apple is red. Fairchild says technically, no it's not. Red is just your perception.
FAIRCHILD: I could change the color of illumination on that apple and make it look green or blue or something - completely different. So the redness isn't a property of the apple. It's a property of the apple in combination with the particular lighting that's on it and the particular observer looking at. You have to have somebody looking at that in order to combine all that information and produce a perception that, you know, we've - in English - learned the word red is associated with that perception.
GREENFIELDBOYCE: He told me this story to show how our brains take in bits of information and combine them to create our experience of color. One night, when his daughter was young, he and his wife decided to have dinner by candlelight. They fed their daughter first.
FAIRCHILD: And my wife made her macaroni and cheese, of course - one of the all-time favorites of an American kid.
GREENFIELDBOYCE: The table was set. The candles were lit, but his daughter took one look and recoiled from her food's color.
FAIRCHILD: And she started almost crying and getting very upset and yelling at us because we gave her the white macaroni and cheese and not the yellow macaroni and cheese. And she - her favorite is the yellow macaroni and cheese.
GREENFIELDBOYCE: Because he studies color perception, Fairchild immediately realized what was going on.
FAIRCHILD: And I said hold on. Stay right there. I can magically turn it into yellow macaroni and cheese. And I walked across the room, and I flipped on the lights.
GREENFIELDBOYCE: Tada - the mac and cheese in her bowl was yellow. But when it was only illuminated by the candlelight, which is very yellow, the light reflecting off her food had looked almost identical to the light reflecting off the white bowl.
FAIRCHILD: She responded to what her eyes created there - the perception her eyes created. And she thought it was white because it matched the bowl.
GREENFIELDBOYCE: Fairchild says an adult would not have made this mistake. We have years of experience with various kinds of illumination. And our brains are constantly adjusting to keep colors looking constant. Besides experience, other things can affect what you see like your unique eyes. Fairchild says even among people with normal color vision -
FAIRCHILD: There are still differences that can be pretty significant.
GREENFIELDBOYCE: The eye has three types of cone cells that respond to different wavelengths of light. But my red cones might be tuned to a narrower range of red wavelengths than yours. And as we age, the lens of the eye gets yellower.
FAIRCHILD: It's like looking through a yellow filter or a yellow piece of glass.
GREENFIELDBOYCE: Then there's fact that about 8 percent of men have some form of color blindness. They see colors, but might, for example, have trouble distinguishing red from green. Either they are missing certain cone types or have cone cells that don't respond normally.
FAIRCHILD: And people do go through life unaware of it. They just think that they can't pick out colors like their wife can or something along those lines.
GREENFIELDBOYCE: Being truly colorblind would mean living in a world without any color. To experience what that would feel like, here's a trick I learned from David Brainard. He's a color scientist at the University of Pennsylvania. He told me that something special happens in very dim light.
DAVID BRAINARD: Part of our eye and brain that allow us to see color is not sensitive enough to pick up the light, and we rather see with our night vision system as you might call it. And that system is colorblind. We don't see distinctions of color.
GREENFIELDBOYCE: That system for dim light relies on the eye's rod cells. And to them everything looks bluish-gray. Brainard says to see this way - go into a closet, close the door and plugged up almost all the cracks to let in just a tiny amount of light. Then, wait for about 20 minutes. He did it recently.
BRAINARD: So I had these kids' picture books, and I sort of looked at what the colors were under normal light. And then, I went in, and I watched them fade to gray and convinced myself that now I couldn't see the differential colors.
GREENFIELDBOYCE: He stresses that light was bouncing off the illustrations in those books and then hitting his eye.
BRAINARD: A physicist measuring spectra would just say yep, spectrum's still there - just less light, but our brains no longer register the information to allow us to see color under those conditions.
GREENFIELDBOYCE: Most of the time, conditions are great for seeing color. And we see lots and lots. Scientists have long wondered - how many colors can we see? They've come up with some estimates that are based on studies of our ability to distinguish between slightly different colors. Brainard says the smart money is on some number of millions.
BRAINARD: Is it 5 million? And is it 1 million? And is it 10 million? I wouldn't want to bet on the answer to that. But, you know, more than a thousand - I'd say less than a billion - probably less than a hundred million.
GREENFIELDBOYCE: 'Cause I think some people might think infinite.
BRAINARD: Yeah. Well, it's not infinite. That's for sure.
GREENFIELDBOYCE: That's not the only unanswered question about color. Because it's a perception, trying to understand color leads to questions that are downright philosophical. If you and I were both looking at, for example, a construction worker hat and saying this is yellow - are we really having the same subjective experience?
BRAINARD: I think we have no way of knowing. I think it's not known because each of us is essentially stuck inside our own brains with respect to the nature of that experience. So your yellow could be like my blue. Your yellow could be like my experience of sound, and my experience of sound could be like your experience of color.
GREENFIELDBOYCE: Brainardsays we learned the names of colors - what kinds of experiences to call yellow or blue. We could talk forever about colors and never disagree. Yet, inside our heads, it could all be very different. Nell Greenfieldboyce, NPR News.
CORNISH: And NPR's visuals team has a lovely companion piece to this series online. It's gorgeous - interactive. It has a lot of great trivia about colors. Seriously, your kids are going to love it. Head over to NPR.org/colors. Transcript provided by NPR, Copyright NPR.