In a large saucepan combine the grapefruit juice, cranberry juice, 3 cups sugar, vanilla bean, cinnamon, zest, and salt. Cook and stir over medium heat until sugar has dissolved. Remove and allow to cool until warm but not hot, about 15 minutes.
Add the cranberries to the mixture and stir. Let stand until room temperature (about 1 hour). Transfer to a bowl; cover and chill 4 hours or overnight.
Drain cranberries well, reserving syrup and vanilla bean. Cover and chill the syrup with the vanilla bean for up to 3 weeks. Remove 1/2 (about 2 cups) of the cranberries. Toss with 1/4 cup red decorating sugar. Toss remaining cranberries with the 1/4 cup white sugar.
Spread the cranberries out in a parchment paper-lined shallow baking pan, keeping the colors separate. Let stand for 1 hour to dry. Store loosely covered at room temperature for up to 1 week.