ΔE 12.4, fair: the same colour family, but not a straight swap. Ruddy Umber is a little lighter, cooler than Earth.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Ruddy Umber is a little lighter, cooler than Earth.
The same difference applies the other way round: Earth is a little darker, 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