The green used on the XJ220 was called Silverstone, Jaguar colour code JD3, almost looks blue under some conditions. The official XJ220 colours were named after famous race circuits - Le Mans Blue, Monza Red, Spa Silver, Daytona Black and Silverstone Green. Give the code to an automotive paint supply store that carries Standox, PPG or similar and they should be able to mix a small quantity for you. Ask them to substitute the finest grade sliver and metallic particles availiable so it looks better in scale.
I just happen to know this because I've recently been looking into the colours for my planned XJ220 build. I've settled on Monza Red, cause I think the car looks looks superb in a dark metallic red.
For all the colour info you could possibly want, try the
Standox formulation database.
See if this direct link works.