ΔE 16.2, loose: different enough that you should pick on purpose. Sap Green is a little darker, much more muted, warmer than Greenskin.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Sap Green is a little darker, much more muted, warmer than Greenskin.
The same difference applies the other way round: Greenskin is a little lighter, much more saturated, cooler.
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 Greenskin on the colour wheel See Sap Green on the colour wheel
All matches: Greenskin equivalents · Sap Green equivalents