Have you ever wondered what it would look like if you took away all of the colors? It wouldn't really be black, white, or gray. People are born blind and they can only describe it as literally being nothing. If you could see at one point, then lost your vision, you might at least dream of shapes and colors but to never see means to imagine something impossible.
What other sense could we simply not be able to fathom because we never had them from the start? Being able to detect magnetic fields come to mind much like a bird. We seem so capable in many ways but also incredibly limited in our visible spectrum. Perhaps some neural link or evolutionary change would make us able to see deeper than what we thought possible.