Mid Feldgrau vs Russian Green 4BO

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Russian Green 4BO is a little darker, more muted than Mid Feldgrau.

Can I use Russian Green 4BO instead of Mid Feldgrau?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Russian Green 4BO is a little darker, more muted than Mid Feldgrau.

Can I use Mid Feldgrau instead of Russian Green 4BO?

The same difference applies the other way round: Mid Feldgrau 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.