The words are "голубой" и "синий". Of course, we understand, that they are closer to each other than to, say, red, but it doesn't change the fact that they are different colours.
> The whole point here is this is about fundamental color concepts
No, the whole point is that no such thing exists. We divide visible light into arbitrary buckets with very blury borders between them and historically these buckets have been very different between different cultures. Nowadays they tend to converge because of globalisation, but they just converge to some common understanding, not "the fundamental" one.
> but it doesn't change the fact that they are different colours.
They are the same hue. That is scientific. It doesn't matter what words you use to divide them -- I am sure you conceptually understand they are the same hue. I even found a comment from a Russian saying [1]:
> I would say that they are two colours that are sufficiently distinct, but I also wouldn't argue against a statement that голубой is a lighter shade of синий.
Again, just like my example with red and pink.
Any Russian painter, for example, would have a very clear idea of a unified "blue" hue, because they have to mix paints. Surely you can't deny that?
You are confusing two things, words and perceptions. The "arbitrary buckets" you describe refer to words. But they don't change our underlying perceptual qualia. We perceive lots of things we don't bother to give names to in order to distinguish them. Our concepts vastly outnumber our words.
And regarding blue specifically -- the brain interprets colors based on the opponent process [2], which includes blue as a one of four fundamental hues. Which argues that it is one of the four most likely colors to have an instinctive perceptual concept for, regardless of whether you give it a word or not.
Why do you give this kind of importance to hue? Hue is not how people divide colour, unless you want to say that white, gray and black are the same colour. The difference between "sky blue" and "royal blue" is just as significant as the difference between orange and brown.
Because hue is scientifically defined and objective. That lets us sidestep all the linguistic stuff so we have something meaningfully perceptual to ground the conversation.
And white, gray and black have no hue at all. They're not the same color -- they have no color at all. The hue is indeterminate. (Even if we call them "colors" colloquially.)
> The whole point here is this is about fundamental color concepts
No, the whole point is that no such thing exists. We divide visible light into arbitrary buckets with very blury borders between them and historically these buckets have been very different between different cultures. Nowadays they tend to converge because of globalisation, but they just converge to some common understanding, not "the fundamental" one.