Old Brass vs Gunmetal

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Gunmetal is a little lighter than Old Brass.

Can I use Gunmetal instead of Old Brass?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Gunmetal is a little lighter than Old Brass.

Can I use Old Brass instead of Gunmetal?

The same difference applies the other way round: Old Brass 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.