Preheat the oven to 350 degrees F (175 degrees C). Butter a 10x15 inch jellyroll pan.

Cook the ground beef in a large heavy skillet over medium heat until evenly browned. Drain off excess grease, and add onion and 2 tomatoes. Continue cooking until onions are tender. Season with salt, pepper, chili powder, and cumin. Stir in refried beans, and cook until heated through.

Lay 6 of the tortillas onto the prepared pan with the edges going well over the sides. Spread all of the bean mixture onto the tortillas. Spread half of the sour cream over the bean layer. Sprinkle with approximately 1/3 of the Colby cheese, and 1/3 of the Monterey Jack cheese. Scatter 1 tablespoon of the green chilies, 1/3 of the green pepper strips, and 1/3 of the red pepper strips followed by 1/3 of the remaining chopped tomato.

Make a layer of only 4 tortillas over the toppings, and spread with remaining sour cream. Top with shredded chicken, then a second 1/3 of both cheeses, red and green bell peppers, chilies, and tomatoes. Arrange the final layer using remaining 4 tortillas as a base, cheeses, peppers, tomatoes, chilies, and ending with shredded cheese on the top. Fold the overhanging edges inward, and secure with toothpicks. Brush exposed tortilla surfaces with melted butter.

Bake for 35 to 45 minutes in the preheated oven, or until heated through, and cheese is melted and bubbly. Remove toothpicks, and let stand for at least 5 minutes before slicing. Spoon picante sauce over according to individual tastes.