A Puzzle Regarding Color

A Puzzle Regarding Color

Color has long intrigued philosophers and others. Is it objective or subjective, or something in between? Is an inverted spectrum possible? What is the nature of logical truths about color? I will raise a different question: do things have the colors they have contingently or necessarily? Is color arbitrary or grounded in facts of nature? For example, could the sky have been green and plants blue? Could blood have been yellow, snow black, coal white, the earth red? I mean by this could things have looked that way; I am not concerned with whether objects could have had different reflectance properties. Things look a certain way color-wise to humans and other animals, but could they just as easily have looked a different way? Is it like driving on the right: could we just as easily have driven on the left (as some other countries do)? Is it completely contingent what colors we bathe the world in? Or is it that specific colors naturally belong to some things and could not be changed without some sort of loss or disruption? If we saw plants not as green but as blue or red or yellow, would there be any loss of accuracy or utility? Are plants naturally seen as green—is this the color they ought to be seen as? I think we are confronted by conflicting intuitions on this question: on the one hand, we feel that plants are correctly seen as green; on the other, there would be no error in seeing them as a different color. Thus, if Martians inverted our color perceptions, they could not be convicted of error or perversity or sub-optimality—they would be as right as we are. The reason is that each color presents the same range of variations and hence distinctions: the same visual information can be presented in blue as in green—and that is all that matters (biologically, intellectually). The color itself is just an arbitrary label, like a proper name. The function of color perception is to allow for visual discrimination, but this can be achieved in a variety of ways; perceivers are not tied down to one color. It would be a form of color prejudice to insist that seeing plants as green is the only viable and veridical way of seeing them; blue would do just as well. Seeing blood as yellow is just as reasonable as seeing it as red. And yet we observe that no such variation obtains: as far we can tell, all animals see the colors of objects the same way, i.e., plants as green and blood as red. The color receptors in the eyes are universal in seeing creatures on Earth: but this seems surprising from an evolutionary perspective, since it would have been just as sensible to evolve blue perception for plants as green perception. We find variation in which side of the road people drive on, which is only to be expected given that this is entirely arbitrary; but we find no variation in what colors are attributed to the world despite the apparent arbitrariness of a given selection. Why? That is the puzzle: why is it theoretically feasible to invert colors and yet this doesn’t happen? Moreover, why does it feel wrong to see plants as anything other than green? Why is seeing plants as green universal and intuitively appropriate, while logically it could have been otherwise without loss or error? Something has to give.

It may be said that this is a case of simple prejudice—custom, what we are used to. We have always seen plants as green and blood as red, so we mistakenly think there is something necessary about this; we are like people who think that driving on the right is the God-given correct way of driving. We have a color superiority complex (prejudiced Martians would have the opposite prejudice). Alternatively, evolution just happened to make an arbitrary choice millions of years ago and has seen no reason to change its mind, even locally. It could have chosen blue or red for plants, but it settled on green and has stuck in its ways. I think neither of these views is plausible: there is something more deep-seated about the way color is perceived. But it is hard to discern what it is exactly—nothing immediately suggests itself. To put it crudely, plants really are green, so it is preferable to see them that way. Compare: it is really better to drive on the right, because actually the sun is less blinding that way. But what is this hidden factor? Could it be that green is actually better suited to encoding subtle differences in things than blue? That would appear to be true of black and white, but on the face of it blue admits of the same degree of variation as green. Is it that things would be more confusing if plants were blue given that the sky is blue—animals would see no sharp distinction? But then why not see the sky as green by way of contrast? Why is blue better for the sky than green? Both can vary in degree of lightness; both can allow clouds to be equally visible. It would be different if we asked why the sky isn’t seen as bright red, because then it would be more limited in its potential variations. So, the puzzle remains: every color seems as good as any other from an informational point of view. Nor does it seem any harder for the brain to produce blue than green perceptions; the colors are equally available and equipotential. Nothing in nature favors one over the other—and yet nature seems determined to stick with a single color-scheme. It is as if it wants animals to see plants as green, even though it has no reason to want that. The colors seem functionally identical, but nature sticks religiously to one scheme rather than another, puzzlingly.

Perhaps we are looking in the wrong place—the informational powers of color perception. What about the emotional and pragmatic connotations of color—the psychology of color? For it does seem true that colors vary in their psychological associations—and not just by habit or custom. Green really is a soothing restful peaceful color, while red is not. Yellow is a joyful light-hearted color. Blue is an attractive charming color (blue eyes). Black is a doom-laden sinister color. White is an optimistic open color. Why this is, we don’t know; it just is. There is a psychology of color—affective, even moral. Orange is felt to be tacky and in poor taste; brown is rather blah. We have favorite colors and least favorite colors. We are not indifferent to color, as if it is nothing but a neutral medium for conveying information. Nature wants us to have good feelings about plants, so it makes us see them as green. Why? Because we have to live with them every day, eat them, lie down on them, or up them. Nature needs to make them a color we are not put off by; it needs to make our brain receptive to them. In the case of blood, it needs to make us wake up and take notice, because the sight of blood is a bad sign. Thus, the colors of nature are designed to mesh with our emotions, desires, and practical decisions—to be psychologically right. Nature (evolution) is cunning in this way: it designs animals to be the best they can be in the circumstances—the most efficient, survival-oriented. All this is carefully planned: the plant world is bathed in green because that is what works best psychologically. Green is inherently likeable, even loveable, so evolution sees to it that we see plants as green. Of course, this is rather mysterious: how can a color be inherently emotional (compare shapes)? And yet it appears to be so: we are hardwired to react to green in certain ways that are conducive to survival, because green intrinsically has a certain affective character. Colors have logical relations built into them, but they also have psychological dispositions built into them. Neither of these things is easy to understand, but they appear to be facts: green is essentially affect-positive, and in a specific way. Not scintillating perhaps (unlike blue) but easy on the eye and brain; not attention-grabbing but mellow and relaxing. When we see green, as with a country landscape, our soul breathes a sigh of relief, a feeling of security and tranquility—unlike a blaze of red flowers or a gorgeously blue sky (too much uplift). The painter chooses his colors carefully, aware of their affective potential; nature chooses its color palette with equal care, properly sensitive to the needs and desires of the creatures living within it. It just wouldn’t feel right to see plants as blue or red, even if this would entail no loss of informational content—it would send the wrong emotional message. Likewise, the bright red of blood delivers a message of alarm and danger—act now! Red is the color of emergency; green of contentment; blue of transcendence (heaven above, piercing blue eyes). Colors are actually very clever, ingeniously designed, magically effective. Natural selection knew what it was doing when it selected the colors of the rainbow, right down to the last detail. Colors are carefully designed adaptive devices not merely dispensable means of conveying objective information. They are not bland. Thus, they are not arbitrarily assigned and interchangeable.

How many colors are there? Estimates vary: I would say basically four: blue, green, red, and yellow (plus black and white). We are told that some animals see colors we don’t see. Let’s say there are ten basic colors on planet Earth. But how many logically possible colors are there—a hundred, a million, infinitely many? Let’s say a lot. Then evolution selected a small subset from the full range, presumably because these are the best ones given the conditions on Earth. They are assigned to objects according to criteria involving psychological requirements (as well as informational requirements). We can assume that this choice was well-motivated—these are the optimal colors for evolutionary purposes. It wasn’t haphazard, random, arbitrary. We thus have a carefully curated world of colors to feast our eyes on (good metaphor)—the best of the best. We should feel good about this: our eyes and brains are recipients of the finest class of colors that money can by—the Rolls-Royces of colors. When you see green you are seeing a finely crafted chromatic machine lovingly perfected over millions of years. You should feel privileged to be privy to such a marvelous spectacle, to live with it day in and day out. Aesthetically speaking, our colors are probably the most beautiful of all (it’s nice to think so anyway); they are not second-rate goods selected by a careless middle man. And each belongs in its proper place. Our visual world is a lot more resplendent and fine-tuned than we might have supposed. We should be thankful.[1]

[1] I almost want to say that colors are a minor miracle—but perhaps I should say that they are major (natural) miracle. They are wonders of the world, demigods, great works of art. We have no idea how they came to be, from what they evolved; but they are with us all the time, glowing like so much pale fire. They came into existence many billions of years after the big bang, themselves flaring into being, and entered the minds of terrestrial creatures. Whenever you see a color, you are seeing a miracle of nature, a veritable show-stopper. I am surprised they have never been used to prove the existence of God! They are much more miraculous than the standard biblical miracles, and we can witness them all the time just by opening our eyes (again, I am speaking of perceived color not the physical basis of color in objects.) They have a kind of intelligence. They evolved but have never gone extinct (that we know of), thus demonstrating their adaptive value. They have helped many a species live to fight another day.