My friend and I talked about this a few weeks ago. What makes us think that we see the same colors? My blue could be someone else's red. Their red could be someone's yellow. So my blue is that person's yellow. And having "warm" and "cool" colors doesn't help, because if someone is brought up believing their "red" color is a cool color, because someone else has learned it to be blue, then they will be calling blue, red. But what if that person is wrong, and it's not blue, but green? Or pink? Thoughts?