ΔE 9.2, close: similar, with a visible difference side by side. USAF Light Blue is a little lighter, more muted, cooler than Bismark's Grave.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). USAF Light Blue is a little lighter, more muted, cooler than Bismark's Grave.
The same difference applies the other way round: Bismark's Grave is a little darker, 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 USAF Light Blue on the colour wheel
All matches: Bismark's Grave equivalents · USAF Light Blue equivalents