Screaming Bell vs Copper

How close are they?

ΔE 16.5, loose: different enough that you should pick on purpose. Copper is a little lighter, more saturated than Screaming Bell.

Can I use Copper instead of Screaming Bell?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Copper is a little lighter, more saturated than Screaming Bell.

Can I use Screaming Bell instead of Copper?

The same difference applies the other way round: Screaming Bell is a little darker, 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.