ΔE 6.6, close: similar, with a visible difference side by side. Russ. AF Dark Green is a little lighter than Midnight Olive.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Russ. AF Dark Green is a little lighter than Midnight Olive.
The same difference applies the other way round: Midnight Olive 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 Midnight Olive on the colour wheel See Russ. AF Dark Green on the colour wheel
All matches: Midnight Olive equivalents · Russ. AF Dark Green equivalents