ΔE 4.6, very close: most people won’t see a difference side by side. Ash Grey is a little darker than Navy Grey. They are different kinds of paint: AMMO by Mig Navy Grey is an ink, glaze or transparent paint and Army Painter Ash Grey is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 5). Ash Grey is a little darker than Navy Grey. They are different kinds of paint.
The same difference applies the other way round: Navy Grey 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 Navy Grey on the colour wheel See Ash Grey on the colour wheel
All matches: Navy Grey equivalents · Ash Grey equivalents