ΔE 6.6, close: similar, with a visible difference side by side. IJA Light Grey Green is a little darker, cooler than Medium Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). IJA Light Grey Green is a little darker, cooler than Medium Grey.
The same difference applies the other way round: Medium Grey is a little lighter, 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 Medium Grey on the colour wheel See IJA Light Grey Green on the colour wheel
All matches: Medium Grey equivalents · IJA Light Grey Green equivalents