I'm certainly no expert either, but as I understand it, the effect of language on color perception is complex and still under debate. See e.g. https://en.wikipedia.org/wiki/Linguistic_relativity_and_the_...

However, the claim the authors of this paper seem to be making is that ancient observers did perceive and distinguish different colors of stars -- as evidenced by the fact that they grouped stars in a way that largely matches modern observations -- but that Betelgeuse is a notable outlier in their observations compared to modern ones. That can't be explained by simply saying that the observers were less perceptive than we are now.

And it's not just one source, but multiple observers from different cultures whose observations corroborate one another.