ΔE 27.4, loose: different enough that you should pick on purpose. Sepia Wash is noticeably lighter, cooler than Brown Wash.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Sepia Wash is noticeably lighter, cooler than Brown Wash.
The same difference applies the other way round: Brown Wash is noticeably darker, 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 Brown Wash on the colour wheel See Sepia Wash on the colour wheel
All matches: Brown Wash equivalents · Sepia Wash equivalents