1. Add sriracha, chili bean oil, lime juice, fish sauce, and sugar in small bowl and whisk until combined. Set aside.
2. Chop bell peppers, carrots, onions, and lettuce and add to large bowl. Mix together and add noodles and protein. Mix well. Add sauce and toss together. (Proportions can be adjusted based on taste preferences.) Garnish with cilantro and green onions. Serve cold.