Readers reply: how can we tell if we see colours in the same way?

The long-running series in which readers answer other readers' questions on subjects ranging from trivial flights of fancy to profound scientific and philosophical concepts

Given that we have a naming convention for colours, we all know that blue is blue. So how do we know that if I saw blue through someone else's eyes, I wouldn't see it as yellow, or pink etc?
David Snell

Please send new questions to nq@theguardian.com.