many languages see blue and green as being 2 different shades of the same colour "grue"
It's not just a language thing, some people have trouble seeing the difference. I don't know if it's an eye or a brain thing, but my father thought the two were almost the same colour, and when I'd point something out as being green, he would say no, that's blue, and later my mom would quietly tell me to ignore what my dad said, because he always gets it wrong! Years later, my father had corrective surgery to his eyes, and said he can see colours "better than ever", but I've never asked him if he can tell blue from green now. I've never had any problem telling them apart, so it must not be hereditary. So I appreciate that it's a problem for some people, even if not for me.
A couple more off topic responses, if that's okay:
there's also the theory that all colors in their entirety are nothing but an illusion of our brains and don't actually exist
Well some people also say, how do you know you're not just a brain in a vat, and everything you've experienced in your entire life is an illusion.
But to address the rest of what you said, the fact that light is just photons and energy, doesn't mean that colours don't exist or have meaning, it just means that for some alternate non-human sentient mind, what photons and energy do, are not decipherable, and don't matter to it. The entire universe would be meaningless matter and energy, if you couldn't perceive the patterns they make.
it wouldn't make it true any more than claiming that 2+2=3
To anyone who says this, I like to say, please solve this: 1.7 + 1.7 = ____, and express the entire equation with all numbers rounded to the nearest whole number. This isn't a cheap trick, it's a reminder that whole and real numbers aren't the same thing, and converting between them, or otherwise rounding numbers without regard to what you're trying to accomplish, has its consequences.