ΔE 9.8, close: similar, with a visible difference side by side. IJA Light Grey Green is a little lighter, warmer than Cockpit Green (IJN).
Usually, if you are not matching paint already on the model. Close match (ΔE 10). IJA Light Grey Green is a little lighter, warmer than Cockpit Green (IJN).
The same difference applies the other way round: Cockpit Green (IJN) 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 Cockpit Green (IJN) on the colour wheel See IJA Light Grey Green on the colour wheel
All matches: Cockpit Green (IJN) equivalents · IJA Light Grey Green equivalents