On older SLs, the interior color code is the first 3-digit group on the 4th line of the data plate on the cross-member in front of the radiator.
I think I have seen 265 mushroom referenced somewhere in my internet travels but I can't recall where. I checked GAHH and World Upholstery with no luck......
Anyway, Leatherique will color match dye to any OEM code.

Hope this helps.