ΔE 19.6, loose: different enough that you should pick on purpose. Ink Skin is a little darker, much more saturated than Mars Black.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Ink Skin is a little darker, much more saturated than Mars Black.
The same difference applies the other way round: Mars Black is a little lighter, much 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 Mars Black on the colour wheel See Ink Skin on the colour wheel
All matches: Mars Black equivalents · Ink Skin equivalents