ΔE 26.5, loose: different enough that you should pick on purpose. Ink Magenta is much more saturated, cooler than Siena.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Ink Magenta is much more saturated, cooler than Siena.
The same difference applies the other way round: Siena is much more muted, 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 Siena on the colour wheel See Ink Magenta on the colour wheel
All matches: Siena equivalents · Ink Magenta equivalents