ΔE 13.0, fair: the same colour family, but not a straight swap. Dark Reaper is a little lighter, more muted, cooler than Mecha Dark Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Dark Reaper is a little lighter, more muted, cooler than Mecha Dark Green.
The same difference applies the other way round: Mecha Dark Green is a little darker, more saturated, 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 Mecha Dark Green on the colour wheel See Dark Reaper on the colour wheel
All matches: Mecha Dark Green equivalents · Dark Reaper equivalents