NSArray *textFields = @[self.emailTextField, self.nameTextField, self.firstNameTextField ... etc];
for (UITextField *textField in textFields) {
    textField.backgroundColor = [UIColor redColor];
}

@interface MyViewController : UIViewController

@property (nonatomic, strong) IBOutletCollection(UITextField) NSArray *textFields;

@end

for (UITextField *textField in self.view.subviews) {
if ([textField isKindOfClass:[UITextField class]]) {
  textField.backgroundColor = [UIColor exampleColor];
 }
}

NSArray *array = @[emailField, nameField, etc...]
    for (UITextField *textField in array)
textField.backgroundColor = [UIColor exampleColor];
}