title: axvspan in subplot not working
body: <p>I try to color in different subplots.</p>
  
  <p>My code:</p>
  
  <pre><code>f, (ax) = plt.subplots(1, 7 , sharey=True, figsize=(14,2))
  color=['g','c','m','y','g','c','m']
  for k in range(7):
      ax[k].axvspan(0,100,facecolor=color[k], alpha = 0.3)
      ax[k].plot(data[k]['x'], data[k]['y'], color=color[k])
      ax[k].set_xscale('log')
  </code></pre>
  
  <p>It does the plot, but not the coloring, though no error is raised. When I don't set_xscale('log'), then it works. 
  Suggestions?</p>