ΔE 15.3, loose: different enough that you should pick on purpose. Green Sky is a little darker, much more saturated than Contagion Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Green Sky is a little darker, much more saturated than Contagion Green.
The same difference applies the other way round: Contagion Green is a little lighter, much more muted.
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 Contagion Green on the colour wheel See Green Sky on the colour wheel
All matches: Contagion Green equivalents · Green Sky equivalents