ΔE 8.2, close: similar, with a visible difference side by side. Ruddy Umber is a little darker, cooler than Earth. They are different kinds of paint: AMMO by Mig Earth is an ink, glaze or transparent paint and Army Painter Ruddy Umber is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Ruddy Umber is a little darker, cooler than Earth. They are different kinds of paint.
The same difference applies the other way round: Earth is a little lighter, 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.
See Earth on the colour wheel See Ruddy Umber on the colour wheel
All matches: Earth equivalents · Ruddy Umber equivalents