ΔE 18.5, loose: different enough that you should pick on purpose. Olive Green is much more muted, warmer than Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Olive Green is much more muted, warmer than Green.
The same difference applies the other way round: Green is much more saturated, cooler.
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 Green on the colour wheel See Olive Green on the colour wheel
All matches: Green equivalents · Olive Green equivalents