ΔE 15.7, loose: different enough that you should pick on purpose. Cursed Blue is a little darker, more muted, cooler than Turquoise Siren.
✓ Two Thin Coats comparison chart lists these two as equivalents.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Cursed Blue is a little darker, more muted, cooler than Turquoise Siren.
The same difference applies the other way round: Turquoise Siren is a little lighter, more saturated, warmer.
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 Turquoise Siren on the colour wheel See Cursed Blue on the colour wheel
All matches: Turquoise Siren equivalents · Cursed Blue equivalents