Comment by just2n

I'm not sure I buy that it means there are more absolute viewable colors there, but rather there are merely different interpretations of the same colors. We do have fairly strong confirmation that our brain doesn't interpret color absolutely but can adjust based on luminescence (see: all examples of shadow illusions) and patterns (see: https://www.youtube.com/watch?v=mf5otGNbkuc), perhaps that's what is meant by a "fourth channel"?