ΔE 15.9, loose: different enough that you should pick on purpose. Deep Magenta is a little lighter, more saturated, warmer than Deep Violet.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Deep Magenta is a little lighter, more saturated, warmer than Deep Violet.
The same difference applies the other way round: Deep Violet is a little darker, more muted, 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 Deep Violet on the colour wheel See Deep Magenta on the colour wheel
All matches: Deep Violet equivalents · Deep Magenta equivalents