you have no way of knowing that what you're seeing is in fact what I am seeing.
Every seeing one only "knows" what "red" is because as a young thing someone showed them innumerable pictures of things and called the things "red." They only "knew" the things were red because people showed them countless pictures of stuff and told them it was "red."
If somehow you could see through my eyes and brain, you may find that my red looks green to you, and evic avers. On that note, Mantis Shrimp. I give you my word that this is relevant.
Edit: Cool, first post on the second page. =D