As this website on auto repair says:
If you are seeing blue smoke from your exhaust this means that your car engine is burning oil.
That's why this color is a very grayish blue; it's a hue similar to the tint you might see in car exhaust if the engine is burning oil, or similar to the color of exhaust you might see in a 2-cycle engine, where oil is mixed with the fuel rather than being stored in a sump.
Companies manufacturing paints, crayons, dyes, or fingernail polish are faced with the unenviable task of naming perhaps dozens of shades of the same base color, and they will often name some shades after everyday objects. Sometimes those names are simply reminiscent of the object they are named after, not exact matches. So banana yellow may not be the exact shade as a real banana, and denim blue might not precisely match your Levi's. In this case, this dull bluish green color had to be named something, and someone was evidently reminded of an oil slick or the blue tint of oil-laced exhaust.
Eggplant? Maybe not exactly, but close enough for a color palatte.