Scaly Highlight vs Light Emerald

How close are they?

ΔE 17.7, loose: different enough that you should pick on purpose. Light Emerald is a little darker, much more muted, cooler than Scaly Highlight.

Can I use Light Emerald instead of Scaly Highlight?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Light Emerald is a little darker, much more muted, cooler than Scaly Highlight.

Can I use Scaly Highlight instead of Light Emerald?

The same difference applies the other way round: Scaly Highlight is a little lighter, much more saturated, 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.