It appears to depend on the specific models. My 1988 W124 looks like it's just the vehicle base coat color (w/o clear), but the WIS indicates that trunk colors in W126s were either Galinite Grey or Deep Dark Grey, depending on model year. Give us chassis number and model year and we may be able to pin it down for you. And yes, spray paints in the correct colors are available from MBz.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't