ΔE 12.2, fair: the same colour family, but not a straight swap. Prussian Blue is more saturated, warmer than Terror Blue-Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Prussian Blue is more saturated, warmer than Terror Blue-Grey.
The same difference applies the other way round: Terror Blue-Grey is more muted, cooler.
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 Terror Blue-Grey on the colour wheel See Prussian Blue on the colour wheel
All matches: Terror Blue-Grey equivalents · Prussian Blue equivalents