ΔE 10.1, fair: the same colour family, but not a straight swap. Legacy Blue is a little darker, more saturated, warmer than Indigo Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Legacy Blue is a little darker, more saturated, warmer than Indigo Blue.
The same difference applies the other way round: Indigo Blue is a little lighter, more muted, 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 Indigo Blue on the colour wheel See Legacy Blue on the colour wheel
All matches: Indigo Blue equivalents · Legacy Blue equivalents