Brazen Copper vs Garnet Alchemy

How close are they?

ΔE 16.8, loose: different enough that you should pick on purpose. Garnet Alchemy is more saturated, cooler than Brazen Copper.

Can I use Garnet Alchemy instead of Brazen Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Garnet Alchemy is more saturated, cooler than Brazen Copper.

Can I use Brazen Copper instead of Garnet Alchemy?

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