ΔE 15.8, loose: different enough that you should pick on purpose. Kantor Blue is a little darker, cooler than Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Kantor Blue is a little darker, cooler than Purple.
The same difference applies the other way round: Purple is a little lighter, 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 Purple on the colour wheel See Kantor Blue on the colour wheel
All matches: Purple equivalents · Kantor Blue equivalents