ΔE 13.6, fair: the same colour family, but not a straight swap. Mahogany Brown is a little darker, more muted, warmer than Undead Skintone.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Mahogany Brown is a little darker, more muted, warmer than Undead Skintone.
The same difference applies the other way round: Undead Skintone is a little lighter, 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 Undead Skintone on the colour wheel See Mahogany Brown on the colour wheel
All matches: Undead Skintone equivalents · Mahogany Brown equivalents