ΔE 9.2, close: similar, with a visible difference side by side. Fern Green is a little darker, more muted than Chromium Oxide Green Dark.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Fern Green is a little darker, more muted than Chromium Oxide Green Dark.
The same difference applies the other way round: Chromium Oxide Green Dark is a little lighter, more saturated.
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 Chromium Oxide Green Dark on the colour wheel See Fern Green on the colour wheel
All matches: Chromium Oxide Green Dark equivalents · Fern Green equivalents