ΔE 17.2, loose: different enough that you should pick on purpose. Blood Thorn is noticeably darker, more saturated, warmer than Magenta.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Blood Thorn is noticeably darker, more saturated, warmer than Magenta.
The same difference applies the other way round: Magenta is noticeably lighter, 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 Magenta on the colour wheel See Blood Thorn on the colour wheel
All matches: Magenta equivalents · Blood Thorn equivalents