ΔE 10.1, fair: the same colour family, but not a straight swap. Grey Blue is a little lighter, more saturated than WWI French Artillery Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Grey Blue is a little lighter, more saturated than WWI French Artillery Grey.
The same difference applies the other way round: WWI French Artillery Grey is a little darker, 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 WWI French Artillery Grey on the colour wheel See Grey Blue on the colour wheel
All matches: WWI French Artillery Grey equivalents · Grey Blue equivalents