Tempest Blue Wash vs Black Wash

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Black Wash is more muted than Tempest Blue Wash.

Can I use Black Wash instead of Tempest Blue Wash?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Black Wash is more muted than Tempest Blue Wash.

Can I use Tempest Blue Wash instead of Black Wash?

The same difference applies the other way round: Tempest Blue Wash is 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.