Stone Green vs Nurgling Green

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Nurgling Green is noticeably darker, cooler than Stone Green.

Can I use Nurgling Green instead of Stone Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Nurgling Green is noticeably darker, cooler than Stone Green.

Can I use Stone Green instead of Nurgling Green?

The same difference applies the other way round: Stone Green is noticeably 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.