ΔE 11.2, fair: the same colour family, but not a straight swap. Mechanicus Standard Grey is a little lighter, more muted than Navy Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Mechanicus Standard Grey is a little lighter, more muted than Navy Blue.
The same difference applies the other way round: Navy Blue is a little darker, more saturated.
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 Blue on the colour wheel See Mechanicus Standard Grey on the colour wheel
All matches: Navy Blue equivalents · Mechanicus Standard Grey equivalents