For travelers to Europe, the rainbow of aperitifs in Mediterranean bars and restaurants has long been a fascination.

There is the extraordinary concoction, the color of Kermit’s blood, served in iced highballs that all four members of that stylish French family are sipping. (Crème de menthe.) Shall I try the bright-yellow stuff that shimmers like liquid gold in the Portofino sunshine? (Limoncello.) And who in their right mind would want to drink anything neon blue on the shores of Juan-les-Pins? (You do. It’s an anise liquor called P’tit Bleu.)