Peel and segment grapefruit and 2 oranges with a sharp knife. Juice remaining orange. Grate 2 teaspoons ginger, and whisk together in a small bowl with honey and the orange juice. Place citrus segments in a serving bowl, and drizzle with the honey mixture. Refrigerate 1 hour, and serve as is or over low-fat vanilla ice cream for a light dessert. Garnish with fresh mint, if desired.