Skull Linen vs Zombie Flesh

How close are they?

ΔE 30.0, loose: different enough that you should pick on purpose. Zombie Flesh is noticeably darker, more saturated than Skull Linen.

Can I use Zombie Flesh instead of Skull Linen?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 30). Zombie Flesh is noticeably darker, more saturated than Skull Linen.

Can I use Skull Linen instead of Zombie Flesh?

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

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.