ΔE 19.1, loose: different enough that you should pick on purpose. Blue Black is a little darker, much more muted than Imperial Navy.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Blue Black is a little darker, much more muted than Imperial Navy.
The same difference applies the other way round: Imperial Navy is a little lighter, much more saturated.
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 Imperial Navy on the colour wheel See Blue Black on the colour wheel
All matches: Imperial Navy equivalents · Blue Black equivalents