ΔE 10.1, fair: the same colour family, but not a straight swap. Cerulean Blue Deep is a little lighter, cooler than Drakenhof Nightshade. They are different kinds of paint: Citadel Drakenhof Nightshade is a wash/shade and Golden Cerulean Blue Deep is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Cerulean Blue Deep is a little lighter, cooler than Drakenhof Nightshade. They are different kinds of paint.
The same difference applies the other way round: Drakenhof Nightshade is a little darker, 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 Drakenhof Nightshade on the colour wheel See Cerulean Blue Deep on the colour wheel
All matches: Drakenhof Nightshade equivalents · Cerulean Blue Deep equivalents