1. In a saucepan, combine rhubarb, sugar (or honey), and 2 tablespoons water. Cook over medium heat for 10 to 20 minutes, stirring occasionally, until rhubarb is soft and jam-like while preserving its bright color and tanginess.
2. Add orange or lemon juice to enhance flavor and color.
3. Puree the cooked rhubarb until smooth and chill in the refrigerator. Thin with a little water if necessary to reach desired consistency.
4. Whisk yogurt with vanilla and thin with milk, half and half, or cream if a creamier texture is preferred.
5. Gently fold chilled rhubarb puree into the yogurt or layer alternately into ice pop molds, swirling lightly with a skewer for a marbled effect.
6. Spoon mixture into ice cube trays, popsicle molds, or disposable cups. Cover molds tightly with plastic wrap or insert popsicle sticks if molds allow.
7. Freeze for at least 4 to 6 hours until firm.
8. To unmold, briefly dip molds in warm water for 15-20 seconds and carefully remove the popsicles.