I took the car in to a Merc specialist yesterday for a service, they phoned up Merc to get the chassis number and the original details. The light poo bumper colour was from factory! The guy's colour coded the grill and wheels to match.
Good luck with that car. Being a lifelong fan of the w126 I have a soft spot for all of them!
Let us know how you get on with all your intended changes for 2017. merc85's car looked a real beauty to me so I am sure yours can be too.