Steampunk Copper vs Arcane Gold

How close are they?

ΔE 24.4, loose: different enough that you should pick on purpose. Arcane Gold is noticeably darker, more saturated, cooler than Steampunk Copper.

Can I use Arcane Gold instead of Steampunk Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Arcane Gold is noticeably darker, more saturated, cooler than Steampunk Copper.

Can I use Steampunk Copper instead of Arcane Gold?

The same difference applies the other way round: Steampunk Copper is noticeably lighter, 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.