Castellax Bronze vs Iridescent Gold Deep (Fine)

How close are they?

ΔE 16.7, loose: different enough that you should pick on purpose. Iridescent Gold Deep (Fine) is noticeably lighter, more muted than Castellax Bronze. They are different kinds of paint: Citadel Castellax Bronze is a metallic and Golden Iridescent Gold Deep (Fine) is a pearl paint, so they won’t behave the same on the model even where the colour is close.

Can I use Iridescent Gold Deep (Fine) instead of Castellax Bronze?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Iridescent Gold Deep (Fine) is noticeably lighter, more muted than Castellax Bronze. They are different kinds of paint.

Can I use Castellax Bronze instead of Iridescent Gold Deep (Fine)?

The same difference applies the other way round: Castellax Bronze is noticeably 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.