ΔE 17.5, loose: different enough that you should pick on purpose. Witch Purple is a little lighter, warmer than Light Magenta.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Witch Purple is a little lighter, warmer than Light Magenta.
The same difference applies the other way round: Light Magenta is a little darker, 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 Light Magenta on the colour wheel See Witch Purple on the colour wheel
All matches: Light Magenta equivalents · Witch Purple equivalents