ΔE 41.6, loose: different enough that you should pick on purpose. Mahogany Ink is noticeably darker, much more muted, warmer than Tenebris Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 42). Mahogany Ink is noticeably darker, much more muted, warmer than Tenebris Blue.
The same difference applies the other way round: Tenebris Blue is noticeably lighter, much more saturated, 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 Tenebris Blue on the colour wheel See Mahogany Ink on the colour wheel
All matches: Tenebris Blue equivalents · Mahogany Ink equivalents