Rich Gold vs Arcane Gold

How close are they?

ΔE 25.2, loose: different enough that you should pick on purpose. Arcane Gold is noticeably lighter, much more muted than Rich Gold.

Can I use Arcane Gold instead of Rich Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Arcane Gold is noticeably lighter, much more muted than Rich Gold.

Can I use Rich Gold instead of Arcane Gold?

The same difference applies the other way round: Rich Gold is noticeably darker, much more saturated.

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.