ΔE 10.5, fair: the same colour family, but not a straight swap. Ruby Red is a little lighter, cooler than Fulgurite Copper.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Ruby Red is a little lighter, cooler than Fulgurite Copper.
The same difference applies the other way round: Fulgurite Copper is a little darker, 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 Fulgurite Copper on the colour wheel See Ruby Red on the colour wheel
All matches: Fulgurite Copper equivalents · Ruby Red equivalents