ΔE 13.4, fair: the same colour family, but not a straight swap. Dwarven Skin is a little lighter, more muted, warmer than Ruddy Umber.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Dwarven Skin is a little lighter, more muted, warmer than Ruddy Umber.
The same difference applies the other way round: Ruddy Umber is a little darker, more saturated, 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 Ruddy Umber on the colour wheel See Dwarven Skin on the colour wheel
All matches: Ruddy Umber equivalents · Dwarven Skin equivalents