Pour chicken broth into crock pot.
Add chicken, onion, red and yellow pepper to a large crock pot.
Season with salt, pepper, cumin, garlic powder and oregano.
Cook on high 2-4 hours or on low 6-8 hours until chicken is cooked through.
Remove chicken from crock pot and shred.
Add crock pot mixture to a large mixing bowl. Add diced tomatoes and Greek yogurt. Stir together.
Pour about 1/2 cup of enchilada sauce into the bottom of a 9x13 pan. It should be just enough sauce to thinly cover the entire pan.
Add chicken filling to tortillas. Place tortillas seam side down in 9x13 pan. Continue until pan is filled. If you have leftover chicken filling, use to make additional enchiladas in a new pan.
Pour 1/2 cup enchilada sauce on top of tortillas. Sprinkle with shredded cheddar cheese. Cover with foil.
Bake for 20 minutes. After 20 minutes, remove foil and bake for 10 more minutes until cheese is melted and bubbly.
Allow enchiladas to rest for 10 minutes before slicing. Top with sliced avocado, cilantro or jalapeno slices before serving.