In a large skillet over medium high heat, brown ground beef and onion until beef is no longer pink. Add in taco seasoning and water, reduce heat to low, and let simmer for 4-5 minutes.
On a large platter, spread out a single layer of tortilla chips. Top with half of the beef mixture, half of the black beans, half of the green and red bell peppers, half of the cheese, and half of the green onions. Repeat layers.
Place nachos in microwave and heat for 60 seconds or until the cheese starts to melt or place in an oven at 350 degrees until the cheese starts to melt.
Top nachos off with sour cream, pico de gallo, and guacamole.