ΔE 9.4, close: similar, with a visible difference side by side. Fog Grey is a little darker, more muted, cooler than Matt Marine Blue. They are different kinds of paint: AMMO by Mig Matt Marine Blue is an ink, glaze or transparent paint and Army Painter Fog Grey is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Fog Grey is a little darker, more muted, cooler than Matt Marine Blue. They are different kinds of paint.
The same difference applies the other way round: Matt Marine Blue is a little lighter, 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 Matt Marine Blue on the colour wheel See Fog Grey on the colour wheel
All matches: Matt Marine Blue equivalents · Fog Grey equivalents