A recent article in The Atlantic piqued my interest but left me very much unsatisfied as to what, if anything, underlies the “pantone” system. So I decided to Google for more info.
The second reference I found was a lot quicker and less “gushy” in getting to the point (or at least to the point that I was interested in), but only slightly more informative.
And the third was clearer about the Pantone distinction – in that it identified the Pantone system as involving many more different pigment types than CMY. But in the end it too failed to fully explain why more than three are needed (and why no finite set, including the Pantone system itself, can ever be “perfect”).
In fact any colour experience can be reproduced with just the three signals corresponding to our three kinds of cone receptors, so the RGB system is capable of producing a light to match any colour that we can ever see.
But that’s the colour of light, not of an object or pigment.
In fact, no actual thing we see, whether object or pigment, actually “has” a colour. It is light that has colour and what pigments do is modify the colour of the light with which they are illuminated by subtracting more of some frequencies than others. The colour of the reflected light then is what we see, but this depends both on the properies of the object and on the spectrum of the ambient light. Since lights of quite different detailed spectrum can produce the same RGB signals in our eye, and there are many different detailed subtractions that can take a given “white” light to any particular value of the RGB signals, it is both possible to have the same pigment look different under two “white” lights which we cannot tell apart and to have two pigments which look the same under one light and different under another – even when the two lights seem to us to be exactly the same. This last is the real weakness of the Pantone Matching System. Unless one is just comparing with other Pantone products, a matching that works under one light might not work under another.