ΔE 7.9, close: similar, with a visible difference side by side. London Grey is more muted than Grey Shadow.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). London Grey is more muted than Grey Shadow.
The same difference applies the other way round: Grey Shadow is 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 Grey Shadow on the colour wheel See London Grey on the colour wheel
All matches: Grey Shadow equivalents · London Grey equivalents