ΔE 26.3, loose: different enough that you should pick on purpose. Shadow Violet is noticeably darker, much more muted, warmer than Xereus Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Shadow Violet is noticeably darker, much more muted, warmer than Xereus Purple.
The same difference applies the other way round: Xereus Purple is noticeably lighter, much more saturated, cooler.
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 Xereus Purple on the colour wheel See Shadow Violet on the colour wheel
All matches: Xereus Purple equivalents · Shadow Violet equivalents