Prussian Blue vs Flat Blue

How close are they?

ΔE 12.0, fair: the same colour family, but not a straight swap. Flat Blue is a little lighter, warmer than Prussian Blue.

Can I use Flat Blue instead of Prussian Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Flat Blue is a little lighter, warmer than Prussian Blue.

Can I use Prussian Blue instead of Flat Blue?

The same difference applies the other way round: Prussian Blue is a little darker, 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.