ΔE 13.2, fair: the same colour family, but not a straight swap. Cerulean Blue Deep is a little darker, more saturated, warmer than Twilight Sky.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Cerulean Blue Deep is a little darker, more saturated, warmer than Twilight Sky.
The same difference applies the other way round: Twilight Sky 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 Twilight Sky on the colour wheel See Cerulean Blue Deep on the colour wheel
All matches: Twilight Sky equivalents · Cerulean Blue Deep equivalents