Red Copper vs Copper Coin

How close are they?

ΔE 30.5, loose: different enough that you should pick on purpose. Copper Coin is a little lighter, much more saturated than Red Copper.

Can I use Copper Coin instead of Red Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Copper Coin is a little lighter, much more saturated than Red Copper.

Can I use Red Copper instead of Copper Coin?

The same difference applies the other way round: Red Copper is a little darker, much 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.