ΔE 6.3, close: similar, with a visible difference side by side. BS Dark Green is more saturated than Olive Drab FS34087.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). BS Dark Green is more saturated than Olive Drab FS34087.
The same difference applies the other way round: Olive Drab FS34087 is more muted.
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 Olive Drab FS34087 on the colour wheel See BS Dark Green on the colour wheel
All matches: Olive Drab FS34087 equivalents · BS Dark Green equivalents