ΔE 8.5, close: similar, with a visible difference side by side. Regiment Grey is a little darker than Grey Blue.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Regiment Grey is a little darker than Grey Blue.
The same difference applies the other way round: Grey Blue is a little lighter.
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 Blue on the colour wheel See Regiment Grey on the colour wheel
All matches: Grey Blue equivalents · Regiment Grey equivalents