ΔE 10.9, fair: the same colour family, but not a straight swap. Martian Ironearth is more saturated than Base Flesh. They are different kinds of paint: AK Interactive Base Flesh is an opaque base/layer paint and Citadel Martian Ironearth is a technical paint or medium, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Martian Ironearth is more saturated than Base Flesh. They are different kinds of paint.
The same difference applies the other way round: Base Flesh is more muted.
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 Base Flesh on the colour wheel See Martian Ironearth on the colour wheel
All matches: Base Flesh equivalents · Martian Ironearth equivalents