Preheat the oven to 350 F. Cook pasta according to package directions. Drain. Melt the butter in a large saucepan over medium-low heat. Add in the flour and cook for a minute to brown.
Add in the milk, salt, pepper, one cup cheddar cheese and pepper jack cheese. Continue to cook over medium-low heat, while whisking constantly until the sauce has thickened.
Mix the sauce with the pasta, and spread the pasta into a greased baking dish. Top with the remaining cheddar cheese. Place olives onto the mac and cheese in a spider pattern. Bake for 25-30 minutes.
