ΔE 36.7, loose: different enough that you should pick on purpose. Sepia Wash is noticeably lighter, more saturated, warmer than Payne’s Grey Wash.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 37). Sepia Wash is noticeably lighter, more saturated, warmer than Payne’s Grey Wash.
The same difference applies the other way round: Payne’s Grey Wash is noticeably darker, more muted, 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 Payne’s Grey Wash on the colour wheel See Sepia Wash on the colour wheel
All matches: Payne’s Grey Wash equivalents · Sepia Wash equivalents