By materialism, I mean the belief that the totality of all in existence is material. That is, particles/waves/energy in the space-time fabric.
If one were to construct a thought experiment that demonstrated there exist things that are independent of matter, then this would weigh heavily against materialism.
Take the following thought experiment: Suppose two twins grow up together. Their physiology is identical.
Twin A experiences the perception, call it PR, of the color red (that is, the material event, call it MR, of photons of a particular wavelength hitting the retina and stimulating neurons). This twin also experiences the perception PB of blue when the material event MB blue photons hit his retina.
However, when the material event MR occurs, Twin B experiences the perception PB. And similarly, Twin B experiences the perception PR when the material event MB occurs.
In all outward appearances, both twins can distinguish between red and blue. If an outside observer person "judged" the differences of perception between Twin A or Twin B, it could still be argued that this judgment itself is only the outside observers unique perception.
Because we could have either alignment in perceptions or no alignment as in the experiment, with no possible material difference, we argue there exists something independent of the material world. That is, at the very least, perception of color is independent of material.
This is far from a new thought experiment, as I've seen popular edu YouTube channels discuss this idea. However, I haven't seen arguments from materialists why this thought experiment doesn't defeat their worldview.
So my question is: What name does this thought experiment have and how do materialists respond to it?