Steampunk Copper vs Bright Bronze

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Bright Bronze is a little darker, much more muted, warmer than Steampunk Copper.

Can I use Bright Bronze instead of Steampunk Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Bright Bronze is a little darker, much more muted, warmer than Steampunk Copper.

Can I use Steampunk Copper instead of Bright Bronze?

The same difference applies the other way round: Steampunk Copper is a little lighter, much more saturated, 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.