ΔE 17.5, loose: different enough that you should pick on purpose. Faded Ultramarine is noticeably lighter, much more muted, warmer than Teclis Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Faded Ultramarine is noticeably lighter, much more muted, warmer than Teclis Blue.
The same difference applies the other way round: Teclis Blue is noticeably darker, much 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 Teclis Blue on the colour wheel See Faded Ultramarine on the colour wheel
All matches: Teclis Blue equivalents · Faded Ultramarine equivalents