title: Kivy Label background color from hex
body: <p>Is it possible to set <code>Label</code> background color as hex value similar to below 
  exaples? </p>
  
  <pre><code>#:import hex kivy.utils.get_color_from_hex
  
  #:set gray_dark hex('#c2c2c2')
  
  &lt;Label@Label&gt;
      background_normal: ''
      bcolor: gray_dark
      canvas.before:
          Color:
              rgba: self.bcolor
          Rectangle:
              pos: self.pos
              size: self.size
  </code></pre>
  
  <p>The only way that works for me is when I set <code>bcolor:</code> to rgba value. Would be fine even when I could define the color as rgba but do it once at the top as below: </p>
  
  <pre><code>#:import hex kivy.utils.get_color_from_hex
  
  #:set gray_dark (0.752, 0.745, 0.745, 1)
  
  &lt;Label@Label&gt;
      background_normal: ''        
      bcolor: gray_dark
      canvas.before:
          Color:
              rgba: self.bcolor
          Rectangle:
              pos: self.pos
              size: self.size
  </code></pre>
  
  <p>Both codes throws an error: </p>
  
  <pre><code>TypeError: 'NoneType' object is not iterable
  </code></pre>
  
  <p>Which is quite obvious as hex is not a list. </p>