ΔE 15.9, loose: different enough that you should pick on purpose. Ultramarine Blue is a little darker, more muted, warmer than Lightning Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Ultramarine Blue is a little darker, more muted, warmer than Lightning Blue.
The same difference applies the other way round: Lightning Blue is a little lighter, more saturated, 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.
See Lightning Blue on the colour wheel See Ultramarine Blue on the colour wheel
All matches: Lightning Blue equivalents · Ultramarine Blue equivalents