ΔE 7.8, close: similar, with a visible difference side by side. Gray Green (Luftwaffe) is a little lighter, warmer than Nocturne Green.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Gray Green (Luftwaffe) is a little lighter, warmer than Nocturne Green.
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.
See Nocturne Green on the colour wheel See Gray Green (Luftwaffe) on the colour wheel
All matches: Nocturne Green equivalents · Gray Green (Luftwaffe) equivalents