What would fry me if I'd received that email - is that he isn't even paying attention to the fact that you were looking for a pastel with a certain look - he's not paying attention to his customer - and he seems to be pushing you to accept the one he sent because he thinks it looks nicer (or at least that is what he wants you to believe so he doesn't have to deal with you again).
If you aren't happy with it insist he take it back at his expense. If you are willing to accept it - then make him give you an acceptable discount. Perhaps tell him you'll have to add special lighting to her tub to make her look like the one you wanted
Oh and find out how the other one died - that would be a concern to me - especially if they were from the same clutch and housed near each other.
Just my two cents.