ΔE 54.9, loose: different enough that you should pick on purpose. Mahogany Ink is noticeably darker, much more saturated than Matt Light Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 55). Mahogany Ink is noticeably darker, much more saturated than Matt Light Grey.
The same difference applies the other way round: Matt Light Grey is noticeably lighter, much 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 Matt Light Grey on the colour wheel See Mahogany Ink on the colour wheel
All matches: Matt Light Grey equivalents · Mahogany Ink equivalents