Decayed Metal vs Obsidian Black

How close are they?

ΔE 10.0, close: similar, with a visible difference side by side. Obsidian Black is a little darker, more muted than Decayed Metal.

Can I use Obsidian Black instead of Decayed Metal?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Obsidian Black is a little darker, more muted than Decayed Metal.

Can I use Decayed Metal instead of Obsidian Black?

The same difference applies the other way round: Decayed Metal 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.