When I teach colorblind students in an elementary class, I subtly review
with them how the paints are arranged because they often keep their
color-blindness private, and it helps if they aren't painting skin
Of course, if they can't distinquish color, you are not going to teach
them to do so, and even color theory is of dubious benefit.
Are you sure the student cannot distinguish darks and lights? If he
recognized values, he could do his painting in black & white, and also
perhaps yellow or orange.