ΔE 8.2, close: similar, with a visible difference side by side. Thunderhawk Blue is a little darker, more muted, cooler than Bismark's Grave.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Thunderhawk Blue is a little darker, more muted, cooler than Bismark's Grave.
The same difference applies the other way round: Bismark's Grave is a little lighter, more saturated, warmer.
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 Thunderhawk Blue on the colour wheel
All matches: Bismark's Grave equivalents · Thunderhawk Blue equivalents