ΔE 8.5, close: similar, with a visible difference side by side. Night Lords Blue is a little lighter, more saturated than Dark Sky.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Night Lords Blue is a little lighter, more saturated than Dark Sky.
The same difference applies the other way round: Dark Sky is a little darker, more muted.
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 Dark Sky on the colour wheel See Night Lords Blue on the colour wheel
All matches: Dark Sky equivalents · Night Lords Blue equivalents