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