ΔE 12.7, fair: the same colour family, but not a straight swap. The Darkness is a little lighter, more muted than Strong Dark Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). The Darkness is a little lighter, more muted than Strong Dark Blue.
The same difference applies the other way round: Strong Dark Blue is a little darker, more saturated.
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 Strong Dark Blue on the colour wheel See The Darkness on the colour wheel
All matches: Strong Dark Blue equivalents · The Darkness equivalents