How do you describe the color “red” to a person who is blind since birth?
I would have him hold his hand against something very warm (stove, near a fire, etc.) and explain that red is a color that looks like that feels. Or feed him something spicy (hot peppers, cinnamon) and say that taste on your tongue is what red looks like. Or when you hear a siren from an ambulance, that sound is what red looks like. This was the technique that Annie Sullivan used with Helen Keller that finally got through to her the relationship between words and meanings. It is also what Eric Stolz’ character in Mask did to show Laura Dern (playing a blind girl) what clouds look like. Hope this helps.