Pastel Blue vs Ghost Green

How close are they?

ΔE 6.1, close: similar, with a visible difference side by side. Ghost Green is cooler than Pastel Blue.

Can I use Ghost Green instead of Pastel Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Ghost Green is cooler than Pastel Blue.

Can I use Pastel Blue instead of Ghost Green?

The same difference applies the other way round: Pastel Blue is 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.