Leafy Green vs Elven Green

How close are they?

ΔE 23.6, loose: different enough that you should pick on purpose. Elven Green is a little darker, much more muted than Leafy Green.

Can I use Elven Green instead of Leafy Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Elven Green is a little darker, much more muted than Leafy Green.

Can I use Leafy Green instead of Elven Green?

The same difference applies the other way round: Leafy Green is a little lighter, much 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.