ΔE 6.8, close: similar, with a visible difference side by side. Dark Sky is a little lighter, warmer than Dark Blue.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Dark Sky is a little lighter, warmer than Dark Blue.
The same difference applies the other way round: Dark Blue is a little darker, 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 Dark Blue on the colour wheel See Dark Sky on the colour wheel
All matches: Dark Blue equivalents · Dark Sky equivalents