title: "ValueError: RGBA values should be within 0-1 range" after upgrading matplotlib
body: <p>I have upgraded to matplotlib 3.0.2 and the script below I used to use for my 3d plots throws this error now: <code>ValueError: RGBA values should be within 0-1 range</code>. Tested with the 2.0.2 version and it works there... Tried to google for similar issues but couldn't find a workaround so asking this smart community for help...</p>
  
  <pre><code>test = pd.DataFrame({'cluster': ["0", "1", "2"],
      'x': [2, 3, 1],
      'y': [10, 5, -2],
      'z': [-10, -5, 2]})
  
  fig = plt.figure(figsize=(7,7))
  
  ax = Axes3D(fig) 
  
  x=test['x']
  y=test['y']
  z=test['z']
  clusters = test['cluster']
  
  ax.scatter(x, y, z, c=clusters, marker='x', cmap='tab20b', depthshade=False)
  ax.set_xlabel('X')
  ax.set_ylabel('Y')
  ax.set_zlabel('Z')
  
  plt.show()
  </code></pre>