Green FS 34258 vs Olive Drab

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Olive Drab is more saturated, cooler than Green FS 34258.

Can I use Olive Drab instead of Green FS 34258?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Olive Drab is more saturated, cooler than Green FS 34258.

Can I use Green FS 34258 instead of Olive Drab?

The same difference applies the other way round: Green FS 34258 is more muted, 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.