Nocturne Green vs Coal Black

How close are they?

ΔE 7.7, close: similar, with a visible difference side by side. Coal Black is a little lighter, warmer than Nocturne Green.

Can I use Coal Black instead of Nocturne Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Coal Black is a little lighter, warmer than Nocturne Green.

Can I use Nocturne Green instead of Coal Black?

The same difference applies the other way round: Nocturne Green is a little darker, cooler.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.