# How many colors?

Is there a way to quantify how many different colors there are?

Is it a matter of perspective?

I suppose I could go into a paint store and starting with a gallon of white paint have them mix in any number or combination of amounts of tints to that can and say there is no end to the number of colors you can create.

However, if my eyesight can’t distinguish between 2 different mixtures is it really a different color?

I’m sure there are color copying machines that can technically reproduce an amazing amount of different colors but there must be a limit as to how many different colors it can “see”?

So is it correct to say that we can make an infinitesimal amounts of color but we can only see a finite amount?

It’s a topic with many byways.

Start here: wiki "Color term."

I have programmed LED lights for theatre productions that are capable of producing 1 billion colors, so the total number must be higher than that.

Well, you’ll have to dive headlong into the physics of what “color” really is.

And, of course, it’s a very, very, tiny part of the electromagnetic spectrum; including from longest wavelength to shortest, radio, microwave, infrared, visible spectrum, ultraviolet, X-rays, and gamma rays.

So, one could argue it’s a continuum of color, providing infinite colors between red and violet. But ever since quantum mechanics showed us that on the smallest scales, perhaps at the Planck length, these wavelengths aren’t so continuous after all.

It’s still a massive number of discrete colors, far more than the human eye could distinguish between, but QM tells us there’s only so many, and it’s not an infinitely divisible continuum of color after all.

Yes, there is a very, very large (not infinite) number of colors, many of which will be indistinguishable (or invisible) to human (but not all) eyes (or instruments).

Try it!

No, the OP’s question is one for psychologists, not physicists. (Technically, it belongs the sub-discipline known as pschophysics, but it is a branch of psychology, not a branch of physics.) You show people objects that differ slightly in their reflectance properties, and test whether or not they can reliably distinguish them. (However, contrary to a common misconception, widespread even amongst color scientists, it does not necessarily follow from this, that colors exist only in the mind. That doctrine depends on highly questionable philosophical assumptions dating back to the 17th century.) Such experimental work has been done. I am afraid I do not know, offhand, the maximum colors people have been found to be able to discriminate, but it is a large number, certainly much greater than the number of different words for colors that any language contains. The proprietary Pantone Color Matching System catalogs 1,114 distinguishable colors, but in fact more can probably be distinguished by careful observers with good “normal” eyesight.

This is irrelevant. Many perfectly real colors, easily distinguished by the human eye, do not occur in the spectrum at all. That is to say, no pure, monochromatic wavelength of light looks that color. These colors only arise from mixtures of wavelengths, or, in some cases, only when other nearby colored surfaces provide necessary contrast. Common examples of such colors are pink, purple, brown, and (believe it or not) red. No monochromatic wavelength looks, to the human eye, to be a pure red; all reddish single, pure wavelengths look either a bit orangey or a little bit violet.

In fact, outside the laboratory (or when looking at a rainbow), we pretty much never see any colors that are monochromatic light wavelengths. Very nearly all the colors we see in the world, including those that appear subjectively to be “pure” and unmixed, are mixtures of light of several wavelengths, usually quite complex mixtures. Also, some colors, notably all the variants of brown, only appear when they do not fill the visual field, but have other nearby areas of a different color to provide suitable contrast. On the other hand, many physically quite different mixtures of wavelengths are indistinguishable to the human eye. This phenomenon is known as metamerism. Metamers are the “same” color, despite being physically very different.

This is quite inconsistent with all normal scientific definitions of “color”.

How so? I was just trying to give a concise summary of the points about wavelength.

Incidentally, neither the RGB system used by color TVs and computer monitors (which produces a wide range of colors by mixing together red, green, and blue light in different proportions), nor the CMYK system used in printing (which produces a range of colors by mixing together cyan, magenta, yellow, and black ink pigments in different proportions) is capable of producing the full range of colors distinguishable by the normal human eye (although each system can give a fairly good approximation).

Which are beside the point, as I explained in post #7. Color is not defined physically, in terms of wavelengths, and the relationship between perceived colors and light wavelengths is very complex.

That’s an understatement! If OP wants to explore this question, here are a couple of Wikipedia articles that explore some quantitative aspects of color perception.

And color perception varies between individuals and may even depend on language, for example:

Yes, I was aware of combined-wavelength colors.

How else could colors be rigorously (scientifically) defined, if not in terms of wavelengths and combinations thereof?

ETA: Wait, you said “perceived.” That’s subjective. Inadequate for a rigorous definition; we need a consistent way to think of colors that includes those people can’t see (but other creatures can).

@njtt

There’s a physics side as well as a physiological side. I don’t dispute that, but to call the physics side irrelevant seems silly.

The OP is asking how many colors there are, and both physics and physiological realms have different, yet related answers. Why not fill in both sides of the story?

How we perceive colors might be described strictly as physiological or psychophysics, yet the part of the EM spectrum we perceive as visible light is certainly in the realm of hard physics.

How can you dispute that?

Read the first part of my post #7 again. Colors cannot be defined except relative to a perceiver. They cannot be defined purely (or even largely) in terms of the physics of light. The attempt to do so results in absurd nonsense such as the claim that “pink does not exist”. However, there is nothing unscientific about defining them relative to perceivers (and, luckily, for the most part, and setting aside physiological defects such as color blindness, all members of a species perceive colors the same), and, in fact, a great deal of rigorous scientific work has been done on that basis. Humans are a lot easier to test, but you can experimentally test the color discrimination abilities of other animals too. (Incidentally, and as an example of such science, contrary to a popular internet meme, mantis shrimp, despite having several more types of color receptors in their eyes than humans, can actually distinguish fewer colors, probably many fewer, than humans can.)

Sorry, but contrary to positivist ideology, not all science reduces smoothly to physics. (Certainly not in practice, given current levels of understanding, but very likely not even in principle.)

Why would pink be nonsensical in terms of the physics of light?

Sure, the nature of the EM spectrum is a matter of physics. The science of color, however, is not a branch of physics (although it draws upon the physics of light). As I already pointed out, the relationship between EM wavelength and color is indirect and very complex and “non-linear” (and, indeed, still not fully understood). Wavelengths are not colors, and colors cannot be defined - the well established, reproducible phenomena of color cannot be explained - purely in terms of wavelengths, or even mixtures of wavelengths.

When you figure out how to create a beam of pink light, or brown light, by mixing together whatever wavelengths you please, get back to me. (The nearest you will get is weak beam of red or orange light.)