ΔE 7.4, close: similar, with a visible difference side by side. Pale Blue Grey is a little lighter, more muted than Gravestone Blue.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Pale Blue Grey is a little lighter, more muted than Gravestone Blue.
The same difference applies the other way round: Gravestone Blue 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 Gravestone Blue on the colour wheel See Pale Blue Grey on the colour wheel
All matches: Gravestone Blue equivalents · Pale Blue Grey equivalents