ΔE 22.8, loose: different enough that you should pick on purpose. Imperial Purple is noticeably darker, much more muted than Coven Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Imperial Purple is noticeably darker, much more muted than Coven Purple.
The same difference applies the other way round: Coven Purple 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.
See Coven Purple on the colour wheel See Imperial Purple on the colour wheel
All matches: Coven Purple equivalents · Imperial Purple equivalents