ΔE 33.7, loose: different enough that you should pick on purpose. Flesh Wash is a little darker, much more muted, warmer than Ancient Sepia.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 34). Flesh Wash is a little darker, much more muted, warmer than Ancient Sepia.
The same difference applies the other way round: Ancient Sepia is a little lighter, much 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 Ancient Sepia on the colour wheel See Flesh Wash on the colour wheel
All matches: Ancient Sepia equivalents · Flesh Wash equivalents