Make each flavor of sorbet as a separate batch, then layer them together in ring molds or dessert bowls.
For each flavor: In a medium bowl, combine juice with sugar and whisk until dissolved. For blood orange and orange sorbets, use 1/2 cup superfine sugar. For lemon sorbet, use 3/4 cup superfine sugar. Refrigerate at least 3 hours. Meanwhile, place 3 loaf pans or shallow containers in the freezer.
Churn each syrup in an ice cream machine according to manufacturer's instructions. Transfer to separate loaf pans and freeze until firm, at least 1 hour or overnight.
To assemble, wrap plastic around bottom and outside of eight 2 1/2-by-2 1/2-inch entremet rings; freeze at least 1 hour. Layer about 1/4 cup of each flavor sorbet into each ring. If softening too quickly, freeze rings in between adding sorbet layers 10. Freeze at least 4 hours and up to overnight.
Chill serving plates in the freezer at least 20 minutes before serving. When ready to serve, warm outside of molds slightly with the palms of your hands, then remove plastic wrap and use a small cardboard circle to push sorbet down, out of mold, and onto chilled plates. Serve immediately, with candied kumquats.