ΔE 8.8, close: similar, with a visible difference side by side. Shadow Flesh is a little lighter, warmer than Ruddy Umber.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Shadow Flesh is a little lighter, warmer than Ruddy Umber.
The same difference applies the other way round: Ruddy Umber is a little darker, 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 Shadow Flesh on the colour wheel
All matches: Ruddy Umber equivalents · Shadow Flesh equivalents