Ultramarine Blue vs Imperium Blue

How close are they?

ΔE 13.4, fair: the same colour family, but not a straight swap. Imperium Blue is a little darker, more saturated than Ultramarine Blue.

Can I use Imperium Blue instead of Ultramarine Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Imperium Blue is a little darker, more saturated than Ultramarine Blue.

Can I use Ultramarine Blue instead of Imperium Blue?

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