ΔE 8.9, close: similar, with a visible difference side by side. BS Dark Earth is a little lighter, warmer than Dark Green Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). BS Dark Earth is a little lighter, warmer than Dark Green Brown.
The same difference applies the other way round: Dark Green Brown 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 Dark Green Brown on the colour wheel See BS Dark Earth on the colour wheel
All matches: Dark Green Brown equivalents · BS Dark Earth equivalents