ΔE 13.5, fair: the same colour family, but not a straight swap. Viking Gold is a little lighter, warmer than Red Copper.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Viking Gold is a little lighter, warmer than Red Copper.
The same difference applies the other way round: Red Copper is a little darker, 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 Red Copper on the colour wheel See Viking Gold on the colour wheel
All matches: Red Copper equivalents · Viking Gold equivalents