ΔE 8.6, close: similar, with a visible difference side by side. Grey Blue is a little lighter, warmer than Shadow Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Grey Blue is a little lighter, warmer than Shadow Grey.
The same difference applies the other way round: Shadow Grey 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 Shadow Grey on the colour wheel See Grey Blue on the colour wheel
All matches: Shadow Grey equivalents · Grey Blue equivalents