ΔE 7.3, close: similar, with a visible difference side by side. USAF Olive Drab is a little lighter, cooler than Dark Boot Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). USAF Olive Drab is a little lighter, cooler than Dark Boot Brown.
The same difference applies the other way round: Dark Boot Brown 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 Dark Boot Brown on the colour wheel See USAF Olive Drab on the colour wheel
All matches: Dark Boot Brown equivalents · USAF Olive Drab equivalents