Dreadful Visage vs Skull Linen

How close are they?

ΔE 9.5, close: similar, with a visible difference side by side. Skull Linen is a little darker, more muted than Dreadful Visage.

Can I use Skull Linen instead of Dreadful Visage?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Skull Linen is a little darker, more muted than Dreadful Visage.

Can I use Dreadful Visage instead of Skull Linen?

The same difference applies the other way round: Dreadful Visage 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.