ΔE 10.2, fair: the same colour family, but not a straight swap. Dark Prussian Blue is more muted, warmer than Deep Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Dark Prussian Blue is more muted, warmer than Deep Blue.
The same difference applies the other way round: Deep Blue is more saturated, cooler.
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 Blue on the colour wheel See Dark Prussian Blue on the colour wheel
All matches: Deep Blue equivalents · Dark Prussian Blue equivalents