title: How to set 0 to white at a uneven color ramp?
body: <p>I have an uneven colour ramp and I want the 0 to be white. All negative colours have to be bluish and all positive colours have to be reddish.
  My current attempted displays the 0 bluish and the 0.7 white. </p>
  
  <p>Is there anyway to set the 0 to white?</p>
  
  <pre><code>import numpy as np
  import matplotlib.colors as colors 
  from matplotlib import pyplot as m
  
  bounds_min = np.arange(-2, 0, 0.1)
  bounds_max = np.arange(0, 4.1, 0.1)
  bounds = np.concatenate((bounds_min, bounds_max), axis=None)       
  norm = colors.BoundaryNorm(boundaries=bounds, ncolors=256)      # I found this on the internet and thought this would solve my problem. But it doesn't...
  m.pcolormesh(xx, yy, interpolated_grid_values, norm=norm, cmap='RdBu_r')
  </code></pre>