ΔE 10.5, fair: the same colour family, but not a straight swap. Potion Green is a little lighter, more muted than Dark Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Potion Green is a little lighter, more muted than Dark Green.
The same difference applies the other way round: Dark Green is a little darker, more saturated.
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 Potion Green on the colour wheel
All matches: Dark Green equivalents · Potion Green equivalents