Light Turquois (Phthalo) vs Light Emerald

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Light Emerald is a little darker, more muted than Light Turquois (Phthalo).

Can I use Light Emerald instead of Light Turquois (Phthalo)?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Light Emerald is a little darker, more muted than Light Turquois (Phthalo).

Can I use Light Turquois (Phthalo) instead of Light Emerald?

The same difference applies the other way round: Light Turquois (Phthalo) 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.