Place the sliced peppers and onions in the bottom of the slow cooker.
Lay the chicken breasts on top of the vegetables.
Add the diced tomatoes.
In a small bowl, combine the chili powder, paprika, garlic powder, onion powder, cumin, salt, and black pepper.
Sprinkle the seasoning mixture evenly over the chicken.
Drizzle with olive oil and lime juice.
Cover and cook on low for 5 to 6 hours or high for 3 to 4 hours.
Remove the chicken and shred it with two forks.
Return the shredded chicken to the slow cooker and stir everything together.
Let cook for an additional 10 minutes.
Serve in warm tortillas with your favorite toppings.