ΔE 10.7, fair: the same colour family, but not a straight swap. Castellax Bronze is a little lighter, more saturated, cooler than Old Gold.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Castellax Bronze is a little lighter, more saturated, cooler than Old Gold.
The same difference applies the other way round: Old Gold is a little darker, more muted, 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.
See Old Gold on the colour wheel See Castellax Bronze on the colour wheel
All matches: Old Gold equivalents · Castellax Bronze equivalents