Castellax Bronze vs Amber Alchemy

How close are they?

ΔE 21.9, loose: different enough that you should pick on purpose. Amber Alchemy is noticeably lighter, cooler than Castellax Bronze.

Can I use Amber Alchemy instead of Castellax Bronze?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Amber Alchemy is noticeably lighter, cooler than Castellax Bronze.

Can I use Castellax Bronze instead of Amber Alchemy?

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