ΔE 10.4, fair: the same colour family, but not a straight swap. IJN Deep Dark Green is a little darker, warmer than Greatcoat Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). IJN Deep Dark Green is a little darker, warmer than Greatcoat Grey.
The same difference applies the other way round: Greatcoat Grey is a little lighter, 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 Greatcoat Grey on the colour wheel See IJN Deep Dark Green on the colour wheel
All matches: Greatcoat Grey equivalents · IJN Deep Dark Green equivalents