Brazen Copper vs Copper Coin

How close are they?

ΔE 33.6, loose: different enough that you should pick on purpose. Copper Coin is much more saturated, warmer than Brazen Copper.

Can I use Copper Coin instead of Brazen Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 34). Copper Coin is much more saturated, warmer than Brazen Copper.

Can I use Brazen Copper instead of Copper Coin?

The same difference applies the other way round: Brazen Copper is much more muted, 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.