How can you explain to a blind man, that an apple is red?

Whether he understands the color as we do depends on whether he has ever had sight in his life or if he was born blind. If he was born blind, there really isn't a way for him to understand colors as we do. It is just a concept to him. I have had many blind friends in the past so I learned this from them.

I would think by expressing feelings and senses, for example, when you feel the sun on your face, you feel brightness, therefore you'd say yellow as a colour, and give a meaning for that specific colour. So you could do the same for red but start off at a different point, to get jist. Dunno, do you know the answer to this question?

just tell him that apple is red and he won't forget it. lol....