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.
Sprinkle the shredded cheddar cheese and crumbled blue cheese (if using) on top of the chicken mixture.
Cover and cook on low for 2-3 hours or until the dip is hot and bubbly, stirring occasionally.
Once done, give it a good stir and garnish with chopped green onions before serving.
Serve warm with tortilla chips, celery sticks, or carrot sticks for dipping.