Dark Shadow vs Extra Dark Green

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Extra Dark Green is a little darker, cooler than Dark Shadow.

Can I use Extra Dark Green instead of Dark Shadow?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Extra Dark Green is a little darker, cooler than Dark Shadow.

Can I use Dark Shadow instead of Extra Dark Green?

The same difference applies the other way round: Dark Shadow is a little 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.