ΔE 37.8, loose: different enough that you should pick on purpose. Vampiric Purple is noticeably darker, much more muted, warmer than Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 38). Vampiric Purple is noticeably darker, much more muted, warmer than Blue.
The same difference applies the other way round: Blue 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 Blue on the colour wheel See Vampiric Purple on the colour wheel
All matches: Blue equivalents · Vampiric Purple equivalents