Nurgling Green vs Pastel Green

How close are they?

ΔE 8.2, close: similar, with a visible difference side by side. Pastel Green is more muted, warmer than Nurgling Green.

Can I use Pastel Green instead of Nurgling Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Pastel Green is more muted, warmer than Nurgling Green.

Can I use Nurgling Green instead of Pastel Green?

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