Colorful Korean Dumplings Mandu

Name: Colorful Korean Dumplings (Mandu)
Ingredients: 1 cup cellophane noodles; 4 cups chopped cabbage; 1 cup chopped onion; 1 cup chopped bell pepper; 1 medium carrot, chopped; 1 tablespoon minced garlic; 1.5 teaspoons salt; 1 pinch ground black pepper; 1 tablespoon olive oil, or more as needed; 1 cup crumbled firm tofu; 2 tablespoons chopped scallions; 2 tablespoons sesame oil; 5 cups all-purpose flour; 1 cup beet juice; 1 large egg, beaten; 1 pinch salt