ΔE 11.8, fair: the same colour family, but not a straight swap. Dark Reaper is a little darker, cooler than French Army Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Dark Reaper is a little darker, cooler than French Army Green.
The same difference applies the other way round: French Army Green is a little lighter, 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 French Army Green on the colour wheel See Dark Reaper on the colour wheel
All matches: French Army Green equivalents · Dark Reaper equivalents