ΔE 14.5, fair: the same colour family, but not a straight swap. Northern Flesh is noticeably lighter, more muted, cooler than Ancient Stone.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Northern Flesh is noticeably lighter, more muted, cooler than Ancient Stone.
The same difference applies the other way round: Ancient Stone is noticeably darker, more saturated, warmer.
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 Ancient Stone on the colour wheel See Northern Flesh on the colour wheel
All matches: Ancient Stone equivalents · Northern Flesh equivalents