title: How to change placeholder color React Native RNPickerSelect
body: <p>I am using this package <a href="https://www.npmjs.com/package/react-native-picker-select" rel="noreferrer">https://www.npmjs.com/package/react-native-picker-select</a></p>
  
  <p>I've tried multiple methods to change the color of the <code>RNPickerSelect</code> placeholder text. But none of them have worked.</p>
  
  <p>Tried the following ways:</p>
  
  <pre class="lang-js prettyprint-override"><code>style = {
    {
      inputIOS: {color: Constants.colour.black},
      inputAndroid: {color: Constants.colour.black},
      placeholderColor: Constants.colour.grey_90,
    }
  }
  </code></pre>
  
  <pre><code>placeholder = { 
    label: placeholderText, 
    value: null, 
    color: Constants.colour.grey_90 
  };
  </code></pre>
  
  <p><strong>UPDATE:</strong></p>
  
  <p>For Android you should set placeholder color in the style proportie like this, hope i can help someone :) :</p>
  
  <pre><code>    style={{
              placeholder: {color: Constants.colour.grey_50},
              inputIOS: { color: Constants.colour.black },
              inputAndroid: { color: Constants.colour.black },
            }}
  </code></pre>