Witchbane Plum vs Dark Plum

How close are they?

ΔE 22.2, loose: different enough that you should pick on purpose. Dark Plum is a little darker, much more muted than Witchbane Plum.

Can I use Dark Plum instead of Witchbane Plum?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Dark Plum is a little darker, much more muted than Witchbane Plum.

Can I use Witchbane Plum instead of Dark Plum?

The same difference applies the other way round: Witchbane Plum 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.