Druchii Violet vs Black Wash

How close are they?

ΔE 40.1, loose: different enough that you should pick on purpose. Black Wash is noticeably darker, much more muted than Druchii Violet.

Can I use Black Wash instead of Druchii Violet?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 40). Black Wash is noticeably darker, much more muted than Druchii Violet.

Can I use Druchii Violet instead of Black Wash?

The same difference applies the other way round: Druchii Violet 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.