ΔE 9.5, close: similar, with a visible difference side by side. Forest Green is a little lighter, cooler than Dark Green.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Forest Green is a little lighter, cooler than Dark Green.
The same difference applies the other way round: Dark Green is a little darker, warmer.
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 Dark Green on the colour wheel See Forest Green on the colour wheel
All matches: Dark Green equivalents · Forest Green equivalents