ΔE 12.5, fair: the same colour family, but not a straight swap. Monastic Green is a little darker, more muted, cooler than Dark Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Monastic Green is a little darker, more muted, cooler than Dark Green.
The same difference applies the other way round: Dark Green is a little lighter, 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 Dark Green on the colour wheel See Monastic Green on the colour wheel
All matches: Dark Green equivalents · Monastic Green equivalents