In a large mixing bowl, combine the shredded chicken, softened cream cheese, buffalo wing sauce, and ranch dressing. Mix until well combined.
Transfer the mixture to a slow cooker and spread it evenly.
Top the mixture with shredded cheddar cheese and crumbled blue cheese, if using.
Cover and cook on low for 2-3 hours or until the dip is heated through and bubbly. Stir occasionally.
Once done, garnish with chopped green onions before serving.
Serve warm with tortilla chips or celery sticks for dipping.