ΔE 11.6, fair: the same colour family, but not a straight swap. Potion Green is a little darker, cooler than Green Sky.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Potion Green is a little darker, cooler than Green Sky.
The same difference applies the other way round: Green Sky is a little lighter, 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 Green Sky on the colour wheel See Potion Green on the colour wheel
All matches: Green Sky equivalents · Potion Green equivalents