ΔE 11.1, fair: the same colour family, but not a straight swap. Mossy Green is a little lighter, more saturated, cooler than WWI German Grey-Green Primer.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Mossy Green is a little lighter, more saturated, cooler than WWI German Grey-Green Primer.
The same difference applies the other way round: WWI German Grey-Green Primer is a little darker, more muted, 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 WWI German Grey-Green Primer on the colour wheel See Mossy Green on the colour wheel
All matches: WWI German Grey-Green Primer equivalents · Mossy Green equivalents