Dead Pink vs Ulthuan Grey

How close are they?

ΔE 18.9, loose: different enough that you should pick on purpose. Ulthuan Grey is a little darker, more muted than Dead Pink.

Can I use Ulthuan Grey instead of Dead Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Ulthuan Grey is a little darker, more muted than Dead Pink.

Can I use Dead Pink instead of Ulthuan Grey?

The same difference applies the other way round: Dead Pink is a little lighter, 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.