
Crème de menthe white is a sweet, mint-flavored liqueur in its clear, colorless form. "Crème" here means high sugar, not cream.
Mint is the flavor and color is the only variable, so the choice is whether the drink should stay pale. Fresh mint gives the aroma without the sugar, which means adding syrup separately and shaking rather than stirring.
Green crème de menthe
Coloring is the only difference. Choose by whether the drink should be green. It tastes alike and turns the drink green, which is the only reason to choose between them.
Peppermint oil is robust and the bottle is colorless, so there is very little here to go wrong. Keep it closed against evaporation and it will taste the same for years.