ΔE 17.6, loose: different enough that you should pick on purpose. Caspian Flesh Wash is noticeably darker, much more muted than Seraphim Sepia.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Caspian Flesh Wash is noticeably darker, much more muted than Seraphim Sepia.
The same difference applies the other way round: Seraphim Sepia is noticeably lighter, much more saturated.
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 Seraphim Sepia on the colour wheel See Caspian Flesh Wash on the colour wheel
All matches: Seraphim Sepia equivalents · Caspian Flesh Wash equivalents