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