ΔE 7.2, close: similar, with a visible difference side by side. Olive Drab is a little lighter than Dark Green. They are different kinds of paint: AMMO by Mig Dark Green is an ink, glaze or transparent paint and Army Painter Olive Drab is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Olive Drab is a little lighter than Dark Green. They are different kinds of paint.
The same difference applies the other way round: Dark Green is a little darker.
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 on the colour wheel See Olive Drab on the colour wheel
All matches: Dark Green equivalents · Olive Drab equivalents