Completely dissolve strawberry flavor gelatin in 2 1/2 cups of the boiling water. Pour 1 1/2 cups of the dissolved gelatin into 6-cup ring mold which has been lightly sprayed with non-stick cooking spray. Chill until set but not firm, about 30 minutes. Meanwhile, chill remaining gelatin in bowl until slightly thickened; gradually blend in 1/3 cup of the yogurt. Spoon over gelatin in mold. Chill until set but not firm, about 15 minutes.
Repeat process with lime flavor gelatin, the remaining 2 1/2 cups boiling water and the remaining 1/3 cup yogurt. Chill 1 1/2 cups dissolved lime flavor gelatin until thoroughly cooled before pouring into mold. (Warm gelatin mixture could soften the layer beneath it and cause mixtures to run together.) Chill until set, about 2 hours.
Makes 6 cups or 12 servings.