Blue Base vs Ultramarine Blue

How close are they?

ΔE 14.4, fair: the same colour family, but not a straight swap. Ultramarine Blue is noticeably lighter, more saturated than Blue Base.

Can I use Ultramarine Blue instead of Blue Base?

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

Can I use Blue Base instead of Ultramarine Blue?

The same difference applies the other way round: Blue Base is noticeably darker, 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.