Have you not seen mask? You just give them a rock that has been boiled. That my friend is red.

Associating senses and feelings with colors doesn't show the color. You could do the same and tell them that it's blue and they wouldn't know the difference.

But why would you lie in the first place? Go watch Mask and learn how to use your humanity.

It has nothing to do with lying, it has to do with how you associate colors with senses and feelings. To quote you for a moment, "give them a rock that has been boiled". By how we are commonly raised and by how society views the world, boiling is associated with the color red. However, for one that does not see color, it is simply boiled. Thus, they could take is as being blue as they wouldn't know the difference. The difference is visual for those with sight and subjective for those without. You might as well be saying that the boiling rock is what the sun looks like.

What I mean to say is to teach them them red you could say hot but you could also place something hot in their hands. Cold for blue etc etc etc.

And that's what I meant by how society views the world. It's still subjective for them. Really, I don't think they care what color cold is referred to as.