ΔE 13.5, fair: the same colour family, but not a straight swap. Imperial Gold is a little darker, more saturated than Steampunk Copper.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Imperial Gold is a little darker, more saturated than Steampunk Copper.
The same difference applies the other way round: Steampunk Copper is a little lighter, more muted.
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 Steampunk Copper on the colour wheel See Imperial Gold on the colour wheel
All matches: Steampunk Copper equivalents · Imperial Gold equivalents