Fry your bacon until crisp, remove from pan and drain on paper towel. Once drained, crumble it and place on another paper towel until needed.
Leave a few tablespoons of bacon grease and add your chopped onion. Stir until onions are tender. Add peppers for a minute or so and then remove from heat and set aside.
Line your slow cooker with an aluminum foil collar and coat with cooking spray. If you need to take a moment to watch the video to see how to do this. Otherwise, you are basically just lining your slow cooker with tin foil until it comes up over the edge of your slow cooker. Your lid will sit inside the tin foil.
Microwave macaroni and oil in bowl at 50 percent power, stirring every minute, until macaroni begin to look toasted and blistered, 5 to 8 minutes.
Prepare your boiling water while you are microwaving the pasta.
Transfer hot macaroni to prepared slow cooker and immediately stir in 2¾ cups boiling water.
Stir in evaporated milk, condensed soup, cheddar, Monterey Jack, mustard, 1 teaspoon pepper, and ½ teaspoon salt.
Add bacon, onions and peppers. Give everything a good stir trying not to puncture the tinfoil.
Cover and cook until macaroni are tender, 1 to 2 hours on high. Season with salt and pepper to taste.