Ultramar Blue vs Dark Prussian Blue

How close are they?

ΔE 13.4, fair: the same colour family, but not a straight swap. Dark Prussian Blue is a little lighter, more muted, warmer than Ultramar Blue.

Can I use Dark Prussian Blue instead of Ultramar Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Dark Prussian Blue is a little lighter, more muted, warmer than Ultramar Blue.

Can I use Ultramar Blue instead of Dark Prussian Blue?

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