ΔE 8.5, close: similar, with a visible difference side by side. US Forest Green is a little lighter than Dark Drab.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). US Forest Green is a little lighter than Dark Drab.
The same difference applies the other way round: Dark Drab 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 Drab on the colour wheel See US Forest Green on the colour wheel
All matches: Dark Drab equivalents · US Forest Green equivalents