Emerald Forest vs Warpstone Glow

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Warpstone Glow is a little darker, more muted than Emerald Forest.

Can I use Warpstone Glow instead of Emerald Forest?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Warpstone Glow is a little darker, more muted than Emerald Forest.

Can I use Emerald Forest instead of Warpstone Glow?

The same difference applies the other way round: Emerald Forest is a little lighter, more saturated.

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.