ΔE 4.6, very close: most people won’t see a difference side by side. Light Brown is a little lighter than Martian Ironearth. They are different kinds of paint: Citadel Martian Ironearth is a technical paint or medium and Vallejo Light Brown is an opaque base/layer 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 5). Light Brown is a little lighter than Martian Ironearth. They are different kinds of paint.
The same difference applies the other way round: Martian Ironearth is a little darker.
ΔE is the colour difference between our two swatch estimates: under 2 is a perfect match (you’d struggle to tell them apart), under 6 very close, under 10 close, under 15 fair, under 20 loose, under 30 very loose, and 30 or more a poor match. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Martian Ironearth on the colour wheel See Light Brown on the colour wheel
All matches: Martian Ironearth equivalents · Light Brown equivalents