Ultramarine Blue vs Cobalt Blue

How close are they?

ΔE 14.3, fair: the same colour family, but not a straight swap. Cobalt Blue is a little lighter, more saturated, cooler than Ultramarine Blue.

Can I use Cobalt Blue instead of Ultramarine Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Cobalt Blue is a little lighter, more saturated, cooler than Ultramarine Blue.

Can I use Ultramarine Blue instead of Cobalt Blue?

The same difference applies the other way round: Ultramarine Blue is a little darker, more muted, warmer.

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.