Place the chicken pieces in the bottom of the slow cooker and season them with salt and black pepper.
Add the red bell pepper chunks, green bell pepper chunks, and pineapple chunks on top of the chicken.
In a small bowl, whisk together the pineapple juice, ketchup, rice vinegar, brown sugar, soy sauce, and cornstarch until smooth.
Pour the sauce mixture over the chicken and vegetables in the slow cooker.
Cover and cook on low for 6 hours or on high for 3 hours until the chicken reaches an internal temperature of 165°F.
Stir gently once before serving to distribute the sauce evenly.