I suspect that one is more likely to understand "green" by realizing that it is a word (originally, a sound) that you have come to associate with memories of visual experiences. To say something is green is to do a comparison between an aspect of the experience of it, and aspects of some of those memories of prior experiences.
I use color as an example because its very distant and theoretically could be many different ways (e.g. your experience of green may not be made of the same stuff my green is). However geometry seems far less arbitrary. Visualizing a square is more specific, the way the lines relate to space in the 2D plane if misrepresented will be wrong. I doubt we visualize such things with 100% accuracy, but we must visualize them to a certain common accuracy, and thats important, common. Basically, as far as experiencing the visual concept of a square, we all experience roughly the same object in our conscious experience. Thats where things can be studied a bit, because the behavior of consciousness given certain logic is likely absolute.
Yes, words are symbols. But when we're talking about consciousness, we're talking about the experience itself, not the association between the word and the experience. And we have no understanding of why or how the experience exists in us.
As for having an opinion, on the other hand, that usually depends on which remarkable circumstance one thinks is less implausible.