We can't rely on the auction house's description as they won't hold themselves responsible for any mistakes in their description or report. The best they would do is to cancel the transaction and give you back the money. The most reliable source is only from Patek's achives record. AFAIK, 3718's dial description is also "ivory, white gold index". Don't know about the black dial Giorgio Seralnoli ediiton, auction house A's description is "enamel" though.
Do you own the 96 enamel? Big congrats! Could you share some more scans? Thanks.
F.