Name the material on the hand, and then put a .png in the folder that is 16x16 and the color you want for the hand (for example, the peach color), and boom. Hand is now that color if you do it correctly. Pretty sure.
you can't change datablocks in-game.
Even if he recolored it peach, it would always be that. Even if the original color of the player's hand is red, it would still be peach.
His problem is not that he can't recolor the model, it's that he can't recolor it to match the player's hand color.
correct me if I'm wrong