ΔE 18.6, loose: different enough that you should pick on purpose. Sepia Wash is noticeably darker, warmer than Necrosis Green Wash.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Sepia Wash is noticeably darker, warmer than Necrosis Green Wash.
The same difference applies the other way round: Necrosis Green Wash is noticeably lighter, 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 Necrosis Green Wash on the colour wheel See Sepia Wash on the colour wheel
All matches: Necrosis Green Wash equivalents · Sepia Wash equivalents