ΔE 16.9, loose: different enough that you should pick on purpose. Mahogany Ink is noticeably lighter, more saturated than Opulentus Black.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Mahogany Ink is noticeably lighter, more saturated than Opulentus Black.
The same difference applies the other way round: Opulentus Black is noticeably darker, more muted.
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 Opulentus Black on the colour wheel See Mahogany Ink on the colour wheel
All matches: Opulentus Black equivalents · Mahogany Ink equivalents