ΔE 31.5, loose: different enough that you should pick on purpose. Ultramarine Blue is a little darker, much more saturated, warmer than Trollblood Base.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 32). Ultramarine Blue is a little darker, much more saturated, warmer than Trollblood Base.
The same difference applies the other way round: Trollblood Base is a little lighter, much more muted, 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 Trollblood Base on the colour wheel See Ultramarine Blue on the colour wheel
All matches: Trollblood Base equivalents · Ultramarine Blue equivalents