Carnelian Skin vs Undead Skintone

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Undead Skintone is noticeably lighter, more saturated, cooler than Carnelian Skin.

Can I use Undead Skintone instead of Carnelian Skin?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Undead Skintone is noticeably lighter, more saturated, cooler than Carnelian Skin.

Can I use Carnelian Skin instead of Undead Skintone?

The same difference applies the other way round: Carnelian Skin is noticeably darker, more muted, warmer.

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.