ΔE 20.9, loose: different enough that you should pick on purpose. Imperial Gold is a little darker, more saturated, warmer than Copper.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Imperial Gold is a little darker, more saturated, warmer than Copper.
The same difference applies the other way round: Copper is a little lighter, 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 Copper on the colour wheel See Imperial Gold on the colour wheel
All matches: Copper equivalents · Imperial Gold equivalents