Deep Blue vs Ultramar Blue

How close are they?

ΔE 12.8, fair: the same colour family, but not a straight swap. Ultramar Blue is a little lighter, warmer than Deep Blue.

Can I use Ultramar Blue instead of Deep Blue?

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

Can I use Deep Blue instead of Ultramar Blue?

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