ΔE 17.8, loose: different enough that you should pick on purpose. Ink Skin is noticeably darker, more saturated than Raw Umber.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Ink Skin is noticeably darker, more saturated than Raw Umber.
The same difference applies the other way round: Raw Umber is noticeably lighter, more muted.
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 Raw Umber on the colour wheel See Ink Skin on the colour wheel
All matches: Raw Umber equivalents · Ink Skin equivalents