ΔE 13.9, fair: the same colour family, but not a straight swap. Viking Grey is noticeably lighter, more saturated than Deep Black.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Viking Grey is noticeably lighter, more saturated than Deep Black.
The same difference applies the other way round: Deep 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 Deep Black on the colour wheel See Viking Grey on the colour wheel
All matches: Deep Black equivalents · Viking Grey equivalents