ΔE 6.9, close: similar, with a visible difference side by side. Desert Olive Green is a little darker, more saturated than IJA Grey Green.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Desert Olive Green is a little darker, more saturated than IJA Grey Green.
The same difference applies the other way round: IJA Grey Green is a little lighter, more muted.
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 IJA Grey Green on the colour wheel See Desert Olive Green on the colour wheel
All matches: IJA Grey Green equivalents · Desert Olive Green equivalents