ΔE 20.0, loose: different enough that you should pick on purpose. Grey Blue is a little darker, more muted, cooler than Violet Coven.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Grey Blue is a little darker, more muted, cooler than Violet Coven.
The same difference applies the other way round: Violet Coven is a little lighter, more saturated, warmer.
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 Violet Coven on the colour wheel See Grey Blue on the colour wheel
All matches: Violet Coven equivalents · Grey Blue equivalents