title: <Select> Placeholder styling
body: <p>So I'm using material-Ui on my react project, I'd like to set a placeholder that's only difference from a selected item is the color being grey instead of black</p>
  
  <pre><code>              &lt;Select
                  name="answer"
                  value={values.answer}
                  onChange={handleChange}
                  onBlur={handleBlur}
                  displayEmpty
                  className={styles.selectEmpty}
                &gt;
                  &lt;MenuItem
                    value=""
                    disabled
                    className={styles.selectPlaceholderText}
                  &gt;
                    Answer
                  &lt;/MenuItem&gt;
                  &lt;MenuItem value={"1"}&gt;1&lt;/MenuItem&gt;
                  &lt;MenuItem value={"2"}&gt;2&lt;/MenuItem&gt;
                  &lt;MenuItem value={"3"}&gt;3&lt;/MenuItem&gt;
                  &lt;MenuItem value={"4"}&gt;4&lt;/MenuItem&gt;
                &lt;/Select&gt;
  </code></pre>
  
  <p>This approach gives me something very close to what I need, the problem is that:</p>
  
  <ul>
  <li>The "Answer" placeholder is there as a disabled list item, I don't even want it in the list.</li>
  <li>It's initially there as I want it, but it's color is black, I'd like to make it grey and styling it in <code>selectPlaceholderText</code> doesn't seem to do the trick.</li>
  </ul>