ΔE 7.8, close: similar, with a visible difference side by side. Blue Grey is a little lighter, more muted than Steel Shadow.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Blue Grey is a little lighter, more muted than Steel Shadow.
The same difference applies the other way round: Steel Shadow is a little darker, more saturated.
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 Steel Shadow on the colour wheel See Blue Grey on the colour wheel
All matches: Steel Shadow equivalents · Blue Grey equivalents