ΔE 17.5, loose: different enough that you should pick on purpose. Prussian Blue is noticeably darker, more saturated than Cold Armour.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Prussian Blue is noticeably darker, more saturated than Cold Armour.
The same difference applies the other way round: Cold Armour is noticeably lighter, 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 Cold Armour on the colour wheel See Prussian Blue on the colour wheel
All matches: Cold Armour equivalents · Prussian Blue equivalents