ΔE 11.6, fair: the same colour family, but not a straight swap. Space Wolves 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 Citadel Space Wolves Grey is a one-coat contrast-style paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Space Wolves 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 Space Wolves Grey on the colour wheel
All matches: Matt Marine Blue equivalents · Space Wolves Grey equivalents