Screaming Skull vs Polished Bone

How close are they?

ΔE 8.1, close: similar, with a visible difference side by side. Polished Bone is more muted, warmer than Screaming Skull.

Can I use Polished Bone instead of Screaming Skull?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Polished Bone is more muted, warmer than Screaming Skull.

Can I use Screaming Skull instead of Polished Bone?

The same difference applies the other way round: Screaming Skull is more saturated, 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.