Ulthuan Grey vs Gypsum White

How close are they?

ΔE 7.3, close: similar, with a visible difference side by side. Gypsum White is more muted than Ulthuan Grey.

Can I use Gypsum White instead of Ulthuan Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Gypsum White is more muted than Ulthuan Grey.

Can I use Ulthuan Grey instead of Gypsum White?

The same difference applies the other way round: Ulthuan Grey is more saturated.

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.