ΔE 8.7, close: similar, with a visible difference side by side. BS Dark Earth is more muted, cooler than NATO Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). BS Dark Earth is more muted, cooler than NATO Brown.
The same difference applies the other way round: NATO Brown is more saturated, 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 NATO Brown on the colour wheel See BS Dark Earth on the colour wheel
All matches: NATO Brown equivalents · BS Dark Earth equivalents