ΔE 27.5, loose: different enough that you should pick on purpose. Ultramarine Blue is much more muted, cooler than Pale Blue Dot.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Ultramarine Blue is much more muted, cooler than Pale Blue Dot.
The same difference applies the other way round: Pale Blue Dot is much 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.
See Pale Blue Dot on the colour wheel See Ultramarine Blue on the colour wheel
All matches: Pale Blue Dot equivalents · Ultramarine Blue equivalents