Cut a thin slice from the top and bottom of each grapefruit; stand fruit upright on a cutting board. With a knife, cut off peel and outer membrane from grapefruit. Cut along the membrane of each segment to remove fruit.
In a large bowl, mix yogurt, lime zest and juice. Layer half of the grapefruit and half of the yogurt mixture into 6 parfait glasses. Repeat layers. Drizzle with honey; top with mint.