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