Yeah, I understand the limitation. But that is an irrelevant objection (is my point), since we already know that the color blind don't see the same colors - and know it at an objective level even (they can't discern them from totally different colors when asked for example).

The study is meant for people with typical vision. Might as well object that they didn't include the blind...

Blind from birth, sure. A bit off topic, but a person who has experienced colors normally and later become blind could still imagine seeing the colors, and that would likely produce the same activation pattern, at least in some parts of the brain.

Then there’s the fact that some people are unable to distinguish between blue and green colors, because their language uses the same word for both. They simply cannot perceive the colors being different. How would they compare?