ΔE 12.4, fair: the same colour family, but not a straight swap. Prussian Blue Hue is a little darker, warmer than Ensign Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Prussian Blue Hue is a little darker, warmer than Ensign Blue.
The same difference applies the other way round: Ensign Blue is a little lighter, 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 Ensign Blue on the colour wheel See Prussian Blue Hue on the colour wheel
All matches: Ensign Blue equivalents · Prussian Blue Hue equivalents