ΔE 12.1, fair: the same colour family, but not a straight swap. The Darkness is noticeably lighter, more saturated than Black Uniform Base.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). The Darkness is noticeably lighter, more saturated than Black Uniform Base.
The same difference applies the other way round: Black Uniform Base 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 Black Uniform Base on the colour wheel See The Darkness on the colour wheel
All matches: Black Uniform Base equivalents · The Darkness equivalents