Spaceship Exterior vs Ulthuan Grey

How close are they?

ΔE 9.3, close: similar, with a visible difference side by side. Ulthuan Grey is a little darker, more saturated than Spaceship Exterior.

Can I use Ulthuan Grey instead of Spaceship Exterior?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Ulthuan Grey is a little darker, more saturated than Spaceship Exterior.

Can I use Spaceship Exterior instead of Ulthuan Grey?

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

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.