ΔE 8.7, close: similar, with a visible difference side by side. Grey Blue is a little lighter than Bismark's Grave.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Grey Blue is a little lighter than Bismark's Grave.
The same difference applies the other way round: Bismark's Grave is a little darker.
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 Bismark's Grave on the colour wheel See Grey Blue on the colour wheel
All matches: Bismark's Grave equivalents · Grey Blue equivalents