Cube chicken and saute with onions and peppers. Season with salt and pepper.
Line the bottom of a 13x9 baking pan with corn tortillas. Then add 1 can of the diced tomatoes with peppers over the tortillas. Do not use all of the juice from the tomatoes. Next layer half the chicken, onion, and pepper mixture over the tomatoes. Then add 1/3 of the cheddar and Colby Jack cheese over the chicken. Then layer with corn tortillas and repeat the above directions once more. Cover the mixture with corn tortillas. On the top layer of tortillas, add diced tomatoes and pepper and sprinkle with remaining cheese.