True Copper vs Castellax Bronze

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Castellax Bronze is a little lighter, more muted than True Copper.

Can I use Castellax Bronze instead of True Copper?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Castellax Bronze is a little lighter, more muted than True Copper.

Can I use True Copper instead of Castellax Bronze?

The same difference applies the other way round: True Copper is a little darker, 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.