Legion Green vs Light Emerald

How close are they?

ΔE 9.6, close: similar, with a visible difference side by side. Light Emerald is a little lighter, more saturated than Legion Green.

Can I use Light Emerald instead of Legion Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Light Emerald is a little lighter, more saturated than Legion Green.

Can I use Legion Green instead of Light Emerald?

The same difference applies the other way round: Legion Green is a little darker, more muted.

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.