Martian Ironearth vs Red Oxide

How close are they?

ΔE 12.6, fair: the same colour family, but not a straight swap. Red Oxide is a little darker, more saturated, cooler than Martian Ironearth. They are different kinds of paint: Citadel Martian Ironearth is a technical paint or medium and Golden Red Oxide is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.

Can I use Red Oxide instead of Martian Ironearth?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Red Oxide is a little darker, more saturated, cooler than Martian Ironearth. They are different kinds of paint.

Can I use Martian Ironearth instead of Red Oxide?

The same difference applies the other way round: Martian Ironearth is a little 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.