Explaining colour to a blind man
I absolutely love this question, It can be taken as a though provoking journey on the way to achieving ZEN, or just a fun question to ponder over. Here's my 'fun' version of the answer.( opinions of what is and isn't fun may vary)
What we 'see' is merely electrical signals interprited by the brain. Even without functioning eyes, the visual cortex in the brain still functions, just in a slightly different way. I have never had the opportunity to ask a blind person if they do 'see' images inside their head, although I have planned an experiment to find out for myself. I have been planning this for a number of years, Basically the idea is to live for a number of weeks in an environment completely isolated from light, a simulated blindness. Unfortunately this is not an easy experiment to setup, hence why I haven't actually achieved it yet, still that is not the point of this article.
Explaining sight, should be no more difficult than explaining any of our other senses, touch, taste, sound, smell. They all cover a broad sensory spectrum. We often describe colour as the red, orange,yellow,green,blue,indigo,violet (It thoroughly annoys me to see rainbow flags missing indigo). We accept these because they are labels that correspond with what we can 'see' Most people are still willing to accept Infra red, Ultra Violet and even Xrays as something that exists even though we cannot 'see' them directly. They are just another portion of the electromagnetic spectrum. But explaining this to someone who has never experienced sight requires some analogies.
We describe sound in its simplest form as high, mid, and low. But again these are just words to cover portions of the frequency spectrum and indeed there are sounds (ultrasonics) that we cant hear.
We can sense Temprature over a large range from cold to hot, we experience A multitude of different smells and tastes, each being able be combined in what is accurately called a pallete, just as we combine colour on a painters pallete.
Colour is just how we differentiate different parts of a spectrum, In the same way we can draw a spectrograph of sound, we could make a colour to sound convertor. Some clever scietists have actually made audio based devices that help blind people 'see'.
If I had to break it down I think the simplest answer would be: