ΔE 14.2, fair: the same colour family, but not a straight swap. Indigo is a little lighter, more muted, warmer than Imperial Navy.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Indigo is a little lighter, more muted, warmer than Imperial Navy.
The same difference applies the other way round: Imperial Navy is a little darker, more saturated, 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 Imperial Navy on the colour wheel See Indigo on the colour wheel
All matches: Imperial Navy equivalents · Indigo equivalents