NSUserDefaults更改后，UITableView和UITableViewCell未更新

Im doing an app that allows the user change the background color and the font of the UITableViewCells on the main viewcontroller of the app. As you may guess this change is set on the settings page of the app, when i navigate back from the settings page back to the main view, the change did not take place. For example if the background of the table view cells is blue, and i change it to red it will only take place if i kill the app on multitasking and restore it or if i scroll the table view. Im doing an app that allows the user change the