ΔE 41.8, loose: different enough that you should pick on purpose. Copper is noticeably darker, more muted, warmer than Bright Gold.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 42). Copper is noticeably darker, more muted, warmer than Bright Gold.
The same difference applies the other way round: Bright Gold is noticeably lighter, more saturated, 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 Bright Gold on the colour wheel See Copper on the colour wheel
All matches: Bright Gold equivalents · Copper equivalents