Red Copper vs Old Copper

How close are they?

ΔE 14.2, fair: the same colour family, but not a straight swap. Old Copper is a little lighter, warmer than Red Copper.

Can I use Old Copper instead of Red Copper?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Old Copper is a little lighter, warmer than Red Copper.

Can I use Red Copper instead of Old 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.