title: Matplotlib ListedColormap transparent color
body: <p>Is possible to use in own colormap transparent color?</p>
  
  <p>This is how I am using custom colormap:</p>
  
  <pre><code>colors = ["#E04848", "#EE6C6C", "#F89090", "#FEB4B4", "#FFD8D8", "#FFFFFF", "#FFFFFF", "#D8D8FF", "#B4B4FF", "#9090FF", "#6C6CFF", "#4848FF"]
  
  cmap= matplotlib.colors.ListedColormap(colors)
  
  m = plt.contourf(xi, yi, zi, levels=boundaries, cmap = cmap, vmin=boundaries_list[0], vmax=boundaries_list[-1])
  
  plt.colorbar(m, spacing="proportional")
  </code></pre>
  
  <p>Is possible to get "#FFFFFF" 100% transparent?</p>