ΔE 12.5, fair: the same colour family, but not a straight swap. Gold is a little lighter, cooler than Old Copper.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Gold is a little lighter, cooler than Old Copper.
The same difference applies the other way round: Old Copper is a little 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.
See Old Copper on the colour wheel See Gold on the colour wheel
All matches: Old Copper equivalents · Gold equivalents