Spaceship Exterior vs Sky Grey

How close are they?

ΔE 7.5, close: similar, with a visible difference side by side. Sky Grey is a little darker than Spaceship Exterior.

Can I use Sky Grey instead of Spaceship Exterior?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sky Grey is a little darker than Spaceship Exterior.

Can I use Spaceship Exterior instead of Sky Grey?

The same difference applies the other way round: Spaceship Exterior is a little lighter.

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.