ΔE 25.5, loose: different enough that you should pick on purpose. Ultramarine Violet is a little lighter, more saturated, warmer than Teclis Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Ultramarine Violet is a little lighter, more saturated, warmer than Teclis Blue.
The same difference applies the other way round: Teclis Blue is a little darker, 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 Teclis Blue on the colour wheel See Ultramarine Violet on the colour wheel
All matches: Teclis Blue equivalents · Ultramarine Violet equivalents