ΔE 16.4, loose: different enough that you should pick on purpose. Azure is noticeably darker, more saturated than Faded Ultramarine.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Azure is noticeably darker, more saturated than Faded Ultramarine.
The same difference applies the other way round: Faded Ultramarine is noticeably lighter, more muted.
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 Faded Ultramarine on the colour wheel See Azure on the colour wheel
All matches: Faded Ultramarine equivalents · Azure equivalents