ΔE 6.1, close: similar, with a visible difference side by side. Nurgling Green is a little darker than Olive Green.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Nurgling Green is a little darker than Olive Green.
The same difference applies the other way round: Olive Green is a little lighter.
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 Nurgling Green on the colour wheel
All matches: Olive Green equivalents · Nurgling Green equivalents