ΔE 8.8, close: similar, with a visible difference side by side. Medium Grey Blue is a little darker, more saturated than Armour Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Medium Grey Blue is a little darker, more saturated than Armour Grey.
The same difference applies the other way round: Armour Grey is a little lighter, more muted.
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 Armour Grey on the colour wheel See Medium Grey Blue on the colour wheel
All matches: Armour Grey equivalents · Medium Grey Blue equivalents