ΔE 10.8, fair: the same colour family, but not a straight swap. Dark Blue is a little darker, more saturated, cooler than Indigo.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Dark Blue is a little darker, more saturated, cooler than Indigo.
The same difference applies the other way round: Indigo is a little lighter, more muted, 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 Indigo on the colour wheel See Dark Blue on the colour wheel
All matches: Indigo equivalents · Dark Blue equivalents