Я бы хотел изменить второе предложение на другой цвет.
UIAlertController * alert=[UIAlertController
alertControllerWithTitle:@"Warning!!!" message:@"This is the first sentence.\r\n\n
This is the second sentence I want a different color.\r\n\n
This is the third sentence.)"
preferredStyle:UIAlertControllerStyleAlert];