Fulgurite Copper vs Copper

How close are they?

ΔE 16.3, loose: different enough that you should pick on purpose. Copper is a little lighter, much more saturated than Fulgurite Copper.

Can I use Copper instead of Fulgurite Copper?

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

Can I use Fulgurite Copper instead of Copper?

The same difference applies the other way round: Fulgurite 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.