ΔE 11.7, fair: the same colour family, but not a straight swap. Old Copper is more saturated, warmer than Emperor Gold.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Old Copper is more saturated, warmer than Emperor Gold.
The same difference applies the other way round: Emperor Gold is more muted, cooler.
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 Emperor Gold on the colour wheel See Old Copper on the colour wheel
All matches: Emperor Gold equivalents · Old Copper equivalents