title: Colors: White if background is DARK and BLACK when is LIGHT
body: <p>I draw some text in a custom Label.</p>
  
  <p>User can modify the label background, but the control shoud accomodate the text visibility in dependence of the specified background.</p>
  
  <p>So, when the background is DARK I want to draw white foreground text, when its LIGHT I want BLACK foreground.</p>
  
  <p>How to "understand" if the color is LIGHT or DARK?</p>