ΔE 3.7, very close: most people won’t see a difference side by side. Our swatches for the two are almost the same. They are different kinds of paint: Citadel Martian Ironearth is a technical paint or medium and Golden Iridescent Copper Light (Fine) is a pearl paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 4). The swatches are almost the same. They are different kinds of paint.
The same difference applies the other way round.
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.
See Martian Ironearth on the colour wheel See Iridescent Copper Light (Fine) on the colour wheel
All matches: Martian Ironearth equivalents · Iridescent Copper Light (Fine) equivalents