Warpstone Glow vs Yellow Green

How close are they?

ΔE 9.6, close: similar, with a visible difference side by side. Yellow Green is a little lighter than Warpstone Glow.

Can I use Yellow Green instead of Warpstone Glow?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Yellow Green is a little lighter than Warpstone Glow.

Can I use Warpstone Glow instead of Yellow Green?

The same difference applies the other way round: Warpstone Glow is a little darker.

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.