Screaming Skull vs Pale Skin

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Pale Skin is noticeably darker, more saturated, warmer than Screaming Skull.

Can I use Pale Skin instead of Screaming Skull?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Pale Skin is noticeably darker, more saturated, warmer than Screaming Skull.

Can I use Screaming Skull instead of Pale Skin?

The same difference applies the other way round: Screaming Skull is noticeably lighter, more muted, cooler.

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.