HI bipin,
As u said he is blind from birth, the persons around him would have thought different colours. So i would ask him if he knows anything about red colour, if he answers yes, then no need to explain, if not then will relate red colour to blood/kumkum/give a red rose and will ask him to feel and tell him this is how it looks because blind people are blessed with other sharp sensations.

Regards,
ajithaa