ΔE 20.3, loose: different enough that you should pick on purpose. Copper is a little darker, more muted, cooler than Gold 79.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Copper is a little darker, more muted, cooler than Gold 79.
The same difference applies the other way round: Gold 79 is a little lighter, more saturated, 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 Gold 79 on the colour wheel See Copper on the colour wheel
All matches: Gold 79 equivalents · Copper equivalents