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