Preheat oven to 350 degrees F. Spray a 9x13-inch baking pan with nonstick cooking spray; set aside.
Heat olive oil in a large skillet over medium-high heat. Sauté bell peppers and onion for 3-5 minutes or until tender. Add garlic and cook for an additional minute.
In a large bowl, combine bell pepper mixture, diced shrimp, cilantro, salt, chili powder, cumin and 1 cup of cheese. Divide mixture evenly between tortillas, roll up and place seam-side down in prepared pan.
To make the cream sauce, melt butter in a large skillet over medium-high heat. Add flour and whisk until combined and cook, stirring continuously, for 1 minute. Slowly whisk in broth until completely smooth. Cook, stirring occasionally, for 5 minutes or until sauce thickens. Remove from heat and mix in Greek yogurt, green chiles and enchilada sauce.
Pour evenly over the top of enchiladas and top with remaining 1⁄2 cup cheese. Bake for 25-30 minutes, or until heated through, then turn oven to high broil and cook for 1-2 more minutes or until golden brown.