ΔE 9.1, close: similar, with a visible difference side by side. IJN Deep Dark Green is a little darker, more muted, warmer than Gray Green (Luftwaffe).
Usually, if you are not matching paint already on the model. Close match (ΔE 9). IJN Deep Dark Green is a little darker, more muted, warmer than Gray Green (Luftwaffe).
The same difference applies the other way round: Gray Green (Luftwaffe) is a little lighter, more saturated, 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 Gray Green (Luftwaffe) on the colour wheel See IJN Deep Dark Green on the colour wheel
All matches: Gray Green (Luftwaffe) equivalents · IJN Deep Dark Green equivalents