ΔE 8.7, close: similar, with a visible difference side by side. Brown Green is a little lighter, warmer than Gengis Khaki.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Brown Green is a little lighter, warmer than Gengis Khaki.
The same difference applies the other way round: Gengis Khaki 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 Gengis Khaki on the colour wheel See Brown Green on the colour wheel
All matches: Gengis Khaki equivalents · Brown Green equivalents