Tom - I don't have the paint code for the chassis, but this could provide some info: https://lotuselan.net/forums/viewtopic.php?f=36&t=19688&start= Sounds like there were different shades of grey used over the years.
If the engine is a med/dark green it's the early Spridget color that's available from Moss and others: https://mossmotors.com/spray-paint-engine-dark-green I'm not sure if there's a code available to mix and spray your own but I'm sure if you had a clean part it could be matched. I have some of the Moss Spridget dark green paint at home that I've used on my old Bugeye Sprite motor and it came out well.
Oh yea, we need some updated photos too!