Morning Sky vs Phthalo Green

How close are they?

ΔE 7.7, close: similar, with a visible difference side by side. Phthalo Green is a little darker, warmer than Morning Sky.

Can I use Phthalo Green instead of Morning Sky?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Phthalo Green is a little darker, warmer than Morning Sky.

Can I use Morning Sky instead of Phthalo Green?

The same difference applies the other way round: Morning Sky is a little lighter, cooler.

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.