Preheat the oven to 350°F (175°C).
In a large skillet over medium-high heat, cook the ground beef until no longer pink, breaking it up as it cooks.
Drain excess grease, then return the beef to the skillet and add the taco seasoning and 3/4 cup water; bring to a boil.
Stir in the cream cheese, reduce heat to low, and simmer about 5 minutes until the cream cheese is melted and the mixture is smooth; transfer to a bowl to cool slightly.
Cook the jumbo pasta shells according to package directions until al dente, drain, then toss with the melted butter to coat and prevent sticking.
Spoon the salsa into the bottom of an 11x7-inch baking dish to form a thin layer.
Fill each buttered shell with a scoop of the beef mixture and arrange the stuffed shells upright in the prepared baking dish.
Drizzle the green enchilada sauce evenly over the shells and bake uncovered for 20 minutes.
Sprinkle the shredded Colby Jack cheese over the shells and bake an additional 10–15 minutes until cheese is melted and bubbly.
Remove from the oven and top with crushed Fritos and dollops of sour cream just before serving.
