smokestone blue does look a little green depending on sunlight/sunset etc, but can also look black at night.
Or Mallard Green that was used on the Escort Cosworth which can look black in different lighting/sunset or at night.

Have you asked the person you bought the shell from to confirm the colour and if the Colour is OE it should be on the Colour tag and logbook mate.
OR take something off like petrol flap or bonnet vent, grill to get the colour matched by a good paint shop.

thx,
Manoj