ΔE 10.2, fair: the same colour family, but not a straight swap. German Gray is a little lighter, cooler than Dark Reaper.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). German Gray is a little lighter, cooler than Dark Reaper.
The same difference applies the other way round: Dark Reaper 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 Reaper on the colour wheel See German Gray on the colour wheel
All matches: Dark Reaper equivalents · German Gray equivalents