With a knife, cut away the peel and white pith of the grapefruit and orange and slice the fruit into rounds.
Arrange the slices on individual plates.
Drizzle with the honey and top with the mint.
Make-Ahead Note: You can cut the peel and pith from the fruit up to 12 hours in advance. Seal tightly in a container and keep in the refrigerator until ready to slice.