ΔE 27.3, loose: different enough that you should pick on purpose. Mahogany Ink is a little darker, much more muted, cooler than Siena.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Mahogany Ink is a little darker, much more muted, cooler than Siena.
The same difference applies the other way round: Siena is a little lighter, much more saturated, 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 Mahogany Ink on the colour wheel
All matches: Siena equivalents · Mahogany Ink equivalents