Green Sky vs Skarsnik Green

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Skarsnik Green is a little darker, much more saturated than Green Sky.

Can I use Skarsnik Green instead of Green Sky?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Skarsnik Green is a little darker, much more saturated than Green Sky.

Can I use Green Sky instead of Skarsnik Green?

The same difference applies the other way round: Green Sky 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.