title: Change UITextField's placeholder text color programmatically
body: <p>I have a <code>UITextField</code> with a placeholder. When the user wants to submit the form and he/she hasn't typed anything in the textfield, I would like the placeholder's text color become red. Here are my questions:</p>
  
  <ul>
  <li>Would that go against Apple's User interface guidelines? I don't want my app to be rejected because of such small detail.</li>
  <li>How I would do it?</li>
  </ul>
  
  <p>I know I can override the method <code>drawPlaceholderInRect:</code> in a subclass of <code>UITextField</code>. But if I did this, the text would be always red and as I wrote before, I would like it to become red depending on a user defined action.</p>
  
  <p>The only solution I can think of is to use a "default" text for my <code>UITextField</code> (the placeholder's text), display it in light grey as long as the user hasn't typed anything and display it in red when I need it. In other words, I would just mock the placeholder's behavior. But of course, this is not very elegant.</p>
  
  <p>Any ideas?</p>