I know what you're saying.

Since I was born, i've been seeing things of the colour Red, and being told that they are Red. The same goes for Blue, Green, Yellow, etc. The same has happened to you, and everyone else.

So when I see an object that I have been taught to recognize as Red, I think 'hmm.. that's Red'. When you see the same thing you will also think 'hmm.. that's Red'. Logically, that makes sense. lol

You and I are both looking at the same 'Red' object and identifying it as Red, because we have learnt that that particular colour is called Red. But, how do I know that you are seeing the same colour that i'm seeing?

You may be seeing what I know as 'Blue', but you are calling it 'Red' because that's what you have been taught to do. So, when we see a Red object, we both identify it as the same colour (Red), but we're not actually seeing the same colour. But, there's no way to tell if we're seeing the same colour or not, because whatever colour we are seeing, we have both been taught to identify it as Red.

I've often wondered about that.. Funnily, i'm nearly always stoned when I do. lol