Prepare the crockpot by spraying it with non-stick cooking spray or lightly greasing it with olive oil.
Layer the sliced onions and bell peppers at the bottom of the crockpot.
Place the chicken breasts on top of the vegetables in the crockpot.
In a small bowl, mix together garlic, chili powder, cumin, paprika, salt, and pepper. Sprinkle this mixture evenly over the chicken.
Drizzle lime juice and olive oil over the top of the chicken.
Cover and cook on low for 6 to 8 hours or on high for 3 to 4 hours, until the chicken is cooked through and tender.
After cooking, shred the chicken directly in the crockpot using two forks.
Stir in the cooked vegetables with the chicken until well combined.
Taste and adjust seasoning as needed, adding more lime juice, salt, or spices if desired.