ΔE 13.5, fair: the same colour family, but not a straight swap. Emerald is noticeably 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 14). Emerald is noticeably darker, more muted, cooler than Dark Green.
The same difference applies the other way round: Dark Green is noticeably 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 Emerald on the colour wheel
All matches: Dark Green equivalents · Emerald equivalents