ΔE 11.1, fair: the same colour family, but not a straight swap. Scarlet is a little lighter, more muted than Alizarin Crimson.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Scarlet is a little lighter, more muted than Alizarin Crimson.
The same difference applies the other way round: Alizarin Crimson is a little darker, more saturated.
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 Alizarin Crimson on the colour wheel See Scarlet on the colour wheel
All matches: Alizarin Crimson equivalents · Scarlet equivalents