Emperor Gold vs Old Bronze

How close are they?

ΔE 7.5, close: similar, with a visible difference side by side. Old Bronze is more muted, cooler than Emperor Gold.

Can I use Old Bronze instead of Emperor Gold?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Old Bronze is more muted, cooler than Emperor Gold.

Can I use Emperor Gold instead of Old Bronze?

The same difference applies the other way round: Emperor Gold is more saturated, warmer.

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.