ΔE 10.4, fair: the same colour family, but not a straight swap. Infantry Blue is noticeably lighter than Dark Prussian Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Infantry Blue is noticeably lighter than Dark Prussian Blue.
The same difference applies the other way round: Dark Prussian Blue is noticeably darker.
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 Dark Prussian Blue on the colour wheel See Infantry Blue on the colour wheel
All matches: Dark Prussian Blue equivalents · Infantry Blue equivalents