ΔE 19.2, loose: different enough that you should pick on purpose. Green Sky is much more saturated, cooler than Kobold Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Green Sky is much more saturated, cooler than Kobold Grey.
The same difference applies the other way round: Kobold Grey is much more muted, 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 Kobold Grey on the colour wheel See Green Sky on the colour wheel
All matches: Kobold Grey equivalents · Green Sky equivalents