ΔE 35.6, loose: different enough that you should pick on purpose. Witching Hour Blue is a little lighter, much more muted, cooler than Eidolon Purple Clear.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 36). Witching Hour Blue is a little lighter, much more muted, cooler than Eidolon Purple Clear.
The same difference applies the other way round: Eidolon Purple Clear is a little darker, much 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 Eidolon Purple Clear on the colour wheel See Witching Hour Blue on the colour wheel
All matches: Eidolon Purple Clear equivalents · Witching Hour Blue equivalents