Fire Opal vs Imperial Gold

How close are they?

ΔE 28.6, loose: different enough that you should pick on purpose. Imperial Gold is noticeably darker, much more muted than Fire Opal.

Can I use Imperial Gold instead of Fire Opal?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Imperial Gold is noticeably darker, much more muted than Fire Opal.

Can I use Fire Opal instead of Imperial Gold?

The same difference applies the other way round: Fire Opal is noticeably lighter, 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.