
Amber bitter liqueur is a bittersweet, usually Italian aperitivo, amber in color, made by flavoring a spirit with bitter and aromatic botanicals.
Another amber bitter
Gran Classico, Biancosarti or Nonino L'Aperitivo swap in at the same measure.
Red bitter aperitivo (Campari-type)
Campari is the easiest to find and works in the same amount. It is a little lower in strength and turns the drink red.
In place of the bitter liqueur it takes the bitter edge away. Two dashes of aromatic bitters bring some back.
As sweet as Campari at less than half the strength. In a stirred, spirit-forward drink it gives a much weaker, softer result.