Cook the noodles according to the package directions.
Meanwhile, heat the oil in a large skillet over high heat. Add the shrimp, snow peas, scallion whites, garlic, and ½ teaspoon salt. Cook, tossing occasionally, until the shrimp are cooked through, 2 to 3 minutes.
Add the oyster sauce, vinegar, soy sauce, and ¼ cup water; cook, tossing, until thickened, 1 to 2 minutes. Add the noodles and toss to combine. Serve sprinkled with the red pepper and scallion greens.