I would still make him aware of his mistake because it pretty basic stuff and if he does not have those basics down in no time there will be a bunch of unhappy customers.

If you are happy with the snake tell him that you are happy and do not want anything from him but that as a courtesy you want to let him know that there is no Mojave in that snake and that if there had been the snake would be white. Maybe that will encourage him to take a step back and start doing some research, though he should have done that before deciding to put two snakes together.