Is black really a color, IMHO it's IR radiation (extension of VIBGYOR) Y / N ?

In all context, additive or subtractive, black is definitively a color. That is a false "tough question" (like "is 0 odd or even", that we don't see any more, but that was frequent once upon a time. Those people, sometimes trolls, thought they were asking a question that desserved endless debate, over ambiguous definitions, when it wasn't).

A color is a spectrum. A function

ℝ⁺→ℝ⁺ that gives the amount of energy for each light frequency.

Additive or subtractive stuff, is just the way you can approach the description of the spectrum using two linear basis of the ℝᴵᴿ space of all possible spectrums (ℝ⁺^ℝ⁺ actually). More specifically the projection of those spectrum on the very limited perception capabilities of human vision. One where you approximate colors using αu₁+βu₂+γu₃, where (α,β,γ) are the additive (RGB) components, and u₁, u₂, u₃ 3 spectrums (the ones of reception by red, green and blue cones of the eye).

Another one where you approximate colors using 1-αu₁-βu₂-γu₃, where (α,β,γ) are the subtractive (cyan,magenta,yellow) components.

Black is just a specific spectrum. The ω↦0 one (for all frequency, energy is 0).

Using additive projection, you can reproduce it (perfectly) using components (0,0,0)

Using subtractive projection, it is harder, and you can't get a perfect black (no wonder why printers, who use subtractive projection use 4 cartridges to print documents meant do be seen by a 3 dimensional color space humans: they need an extra cartridges to print black, because you can't do a good black just with the 3 primary colors).

Now, you could claim that absence of light is not a spectrum. As you could claim that immobility is not a speed (even tho it is just speed 0) or that absolute 0K is not a temperature.

But that would be a little bit being smart ***.

Besides, I get why one can say "using additive representation, (0,0,0) is absence of color, whereas (r,g,b), with r≠0,g≠0 and/or b≠0 is. Using subtractive representation, black is not (0,0,0), so it is a color".

But if I want to play that game, I could also claim that, on the contrary, black is just one of the many color that you can represent with (r,g,b) additive space, but you can't represent it perfectly with CMY color space. So it is not a color, in subtractive projection, if you need to invent a fourth dimension to a 4 dimensional space to represent it.

But again, that applies to those specific color representations. Not to the color itself.

Black is a color.

It is from a scientific point of view.

And it is from a everyday speaking point of view.

This is not one of those debates where you can get people fighting because science disagree with common sense.

(Tho you will get people fighting. When I started writing, there was one answer to your question. Coming from someone I almost always agree with. And that answer contradicts mine. Years ago, you could get even educated people fighting on that "is 0 odd or even" false debate. Never got why it worked, but it worked)

Neither white nor black are colours, from a scientific point of view.

Well, it's not a sound. It's not a taste. Not a smell. Not a shape, size, or texture. If it's not a color, then what is it?

Humans don't distinguish infrared from ultraviolet

some other species do

No it isn't, because black body radiation can be in any frequency and in theory an object at absolute zero would still be black, i.e. it would radiate nothing.

In everyday life, black is a color: I bought a lovely black car yesterday. In physics, black is the absence of light absorption, so it is not a color. Astronomers going to the moon saw dark space and no colors around them.

In additive colour mixing - differing amounts of Red, Green & Blue light - black is simply a lack of any light rather than a colour.

However, with subtractive mixing - paints, dyes & suchlike that show colour when illuminated by white light - black is a paint, pigment or dye etc. which absorbs (nearly) all light, so the result is little reflected light of any colour.

In that context, black is definitely a colour!