Obsidian Skin vs Slate Grey

How close are they?

ΔE 7.0, close: similar, with a visible difference side by side. Slate Grey is a little lighter than Obsidian Skin.

Can I use Slate Grey instead of Obsidian Skin?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Slate Grey is a little lighter than Obsidian Skin.

Can I use Obsidian Skin instead of Slate Grey?

The same difference applies the other way round: Obsidian Skin is a little darker.

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.