ΔE 19.8, loose: different enough that you should pick on purpose. Deep Magenta is noticeably lighter, more saturated, warmer than Shadow Violet.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Deep Magenta is noticeably lighter, more saturated, warmer than Shadow Violet.
The same difference applies the other way round: Shadow Violet is noticeably 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 Shadow Violet on the colour wheel See Deep Magenta on the colour wheel
All matches: Shadow Violet equivalents · Deep Magenta equivalents