ΔE 6.7, close: similar, with a visible difference side by side. Flat Green is more saturated, warmer than Olive Green.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Flat Green is more saturated, warmer than Olive Green.
The same difference applies the other way round: Olive Green is more muted, 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 Olive Green on the colour wheel See Flat Green on the colour wheel
All matches: Olive Green equivalents · Flat Green equivalents