ΔE 7.5, close: similar, with a visible difference side by side. Olive Drab is a little lighter, cooler than Medium Drab.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Olive Drab is a little lighter, cooler than Medium Drab.
The same difference applies the other way round: Medium Drab is a little darker, 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 Medium Drab on the colour wheel See Olive Drab on the colour wheel
All matches: Medium Drab equivalents · Olive Drab equivalents