ΔE 15.4, loose: different enough that you should pick on purpose. Midnight Purple is a little darker, more saturated than The Darkness.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Midnight Purple is a little darker, more saturated than The Darkness.
The same difference applies the other way round: The Darkness is a little lighter, 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 The Darkness on the colour wheel See Midnight Purple on the colour wheel
All matches: The Darkness equivalents · Midnight Purple equivalents