Field Green FS 34097 vs Elysian Green

How close are they?

ΔE 15.9, loose: different enough that you should pick on purpose. Elysian Green is a little lighter, more saturated, cooler than Field Green FS 34097.

Can I use Elysian Green instead of Field Green FS 34097?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Elysian Green is a little lighter, more saturated, cooler than Field Green FS 34097.

Can I use Field Green FS 34097 instead of Elysian Green?

The same difference applies the other way round: Field Green FS 34097 is a little darker, 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.