ΔE 17.5, loose: different enough that you should pick on purpose. Black Wash is a little darker, much more muted than Muddy Wash.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Black Wash is a little darker, much more muted than Muddy Wash.
The same difference applies the other way round: Muddy Wash is a little 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 Muddy Wash on the colour wheel See Black Wash on the colour wheel
All matches: Muddy Wash equivalents · Black Wash equivalents