title: How can I get the default maximumTrackTintColor for a UISlider
body: <p>I'm trying to make a UISlider have the tint colour on the right side and the dull colour on the  left side (swap them around)</p>
  
  <p>I'm able to get the correct colour on the right with</p>
  
  <pre><code>mySlider.maximumTrackTintColor = self.view.tintColor
  </code></pre>
  
  <p>but I don't know how to get the grey colour in order to set the <code>minimumTrackTintColor</code>.</p>
  
  <p>I tried</p>
  
  <pre><code>mySlider.minimumTrackTintColor = mySlider.maximumTrackTintColor
  </code></pre>
  
  <p>before I set the <code>maximumTrackTintColor</code> but that doesn't work because <code>mySlider.maximumTrackTintColor</code> returns nil if a custom colour hasn't been set.</p>