The code may appear as letters or numbers. They used both, it's a Rover/Land Rover thing.
Although there is a perfectly good part of the VIN plate (see above) for the code a few years LR couldn't be bothered to put it on.
In those cases you MIGHT be able to get the code from a franchised LR dealer's parts dept if you give them your reg or VIN number.
659 is one code for Bonatti Grey/Pewter Grey. Two names, same colour.