If I’m thinking one color for a young man, I think grey. Grey can be a little more casual than black. And no to brown IMO.
@conmama Free advice from me. Do NOT give this as a surprise gift. I have a son. He really has his own sense of style, and prefers to choose his own clothes. One year, I did give him a shopping trip for clothes while,we were together.
You might want to consider giving your son a trip to get a sports jacket, or some clothing. You can wrap up pictures of some of your ideas, and the stores from which they can be purchased. Then plan a half day outing so he can try them on, see how they fit, and choose the colors and fabrics he likes and will therefore likely wear.