Celestial Azure vs Ultramarine Blue

How close are they?

ΔE 14.8, fair: the same colour family, but not a straight swap. Ultramarine Blue is more muted, cooler than Celestial Azure.

Can I use Ultramarine Blue instead of Celestial Azure?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Ultramarine Blue is more muted, cooler than Celestial Azure.

Can I use Celestial Azure instead of Ultramarine Blue?

The same difference applies the other way round: Celestial Azure is more saturated, 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.