Emperor Gold vs Dark Iron

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Dark Iron is much more muted, warmer than Emperor Gold.

Can I use Dark Iron instead of Emperor Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Dark Iron is much more muted, warmer than Emperor Gold.

Can I use Emperor Gold instead of Dark Iron?

The same difference applies the other way round: Emperor Gold is much more saturated, cooler.

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.