ΔE 3.0, very close: most people won’t see a difference side by side. Muddy Brown is warmer than Mordant Earth. They are different kinds of paint: Citadel Mordant Earth is a technical paint or medium and Reaper Muddy 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 3). Muddy Brown is warmer than Mordant Earth. They are different kinds of paint.
The same difference applies the other way round: Mordant Earth is 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.
See Mordant Earth on the colour wheel See Muddy Brown on the colour wheel
All matches: Mordant Earth equivalents · Muddy Brown equivalents