ΔE 13.0, fair: the same colour family, but not a straight swap. Ruby Red is a little lighter, more muted than Pure Copper.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Ruby Red is a little lighter, more muted than Pure Copper.
The same difference applies the other way round: Pure Copper is a little darker, more saturated.
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 Pure Copper on the colour wheel See Ruby Red on the colour wheel
All matches: Pure Copper equivalents · Ruby Red equivalents