Castellax Bronze vs Heirloom Gold

How close are they?

ΔE 20.5, loose: different enough that you should pick on purpose. Heirloom Gold is noticeably lighter, cooler than Castellax Bronze.

Can I use Heirloom Gold instead of Castellax Bronze?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Heirloom Gold is noticeably lighter, cooler than Castellax Bronze.

Can I use Castellax Bronze instead of Heirloom Gold?

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.