Those codes are both a bit odd. Take the L off (it stands for Lackierung, meaning "finish", or lacquer if you prefer) and most VAG codes are xdy, where x used to be a country/origin code (S was Seat/Spain) d is a digit indicating the colour in the RAL system and the final letter y is just a code letter.
Neither 1BC nor Z72 fits this structure, meaning they are either older codes (like 041 Black) or there's a typo in there somewhere.
The middle digit 7 is right for a grey or silver finish.
Moving to the names, Anthrazit = Anthracite = coal coloured, more or less. This will be a dark metallic colour, I'd expect.
Plata R is Spanish for Silver R (plata as in plate, like the river between Argentina and Uraguay), and I'd expect that to be a lighter colour.
Neither of those colours has ever appeared on Seats, as far as I know, unless it's a long way back.