ΔE 13.3, fair: the same colour family, but not a straight swap. Indigo Sky is more muted, warmer than Calgar Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Indigo Sky is more muted, warmer than Calgar Blue.
The same difference applies the other way round: Calgar Blue is 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 Calgar Blue on the colour wheel See Indigo Sky on the colour wheel
All matches: Calgar Blue equivalents · Indigo Sky equivalents