Eternal Hunt vs Russian Green 1

How close are they?

ΔE 9.0, close: similar, with a visible difference side by side. Russian Green 1 is a little lighter, more muted than Eternal Hunt.

Can I use Russian Green 1 instead of Eternal Hunt?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Russian Green 1 is a little lighter, more muted than Eternal Hunt.

Can I use Eternal Hunt instead of Russian Green 1?

The same difference applies the other way round: Eternal Hunt is a little darker, 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.