Ulthuan Grey vs The White

How close are they?

ΔE 18.7, loose: different enough that you should pick on purpose. The White is noticeably lighter, more muted than Ulthuan Grey.

Can I use The White instead of Ulthuan Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). The White is noticeably lighter, more muted than Ulthuan Grey.

Can I use Ulthuan Grey instead of The White?

The same difference applies the other way round: Ulthuan Grey is noticeably darker, 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.