It doesn't matter how one person perceives "red". What matter is they can consistently agree with other about what things are red what not. It is a bit like a

It doesn't matter how one person perceives "red". What matter is they can consistently agree with other about what things are red what not. It is a bit like a web-page with many dom-elements on it, each having its own id. The id is like our perceptions. The id is arbitrary but what matters is that the same id always refers to the same dom-element. I mean I don't even know what I perceive when I perceive red. I just perceive and use the id "red" for it. The thing is that in our brain there is some kind of an id associated with our experience of redness. When we experience it we say hey I recognize this experience as something familiar, so I will use the same id 'red' to describe it as I have before.