Ultramarine Blue vs Dark Blue

How close are they?

ΔE 11.9, fair: the same colour family, but not a straight swap. Dark Blue is noticeably darker, warmer than Ultramarine Blue.

Can I use Dark Blue instead of Ultramarine Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Dark Blue is noticeably darker, warmer than Ultramarine Blue.

Can I use Ultramarine Blue instead of Dark Blue?

The same difference applies the other way round: Ultramarine Blue is noticeably lighter, 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.