change color for first level of contourf
<p>I'm using this script to plot a Ramachandran plot (the kind of plot is not really relevant here, what matters is the outputted graph):</p>

<pre><code>#!/usr/bin/python
# coding: utf-8

"""
Script to plot a heat map of the dihedral angles
http://stackoverflow.com/questions/26351621/turn-hist2d-output-into-contours-in-matplotlib
"""

import sys
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import LogNorm

# print(sys.argv[1])

frame, x, y = np.loadtxt(sys.argv[1], unpack=True)

fig = plt.figure(1)
ax = plt.subplot(111)


counts, ybins, xbins, image = plt.hist2d(x, y, bins=180, norm=LogNorm())
plt.clf()
plt.contourf(counts.transpose(), 10, extent=[xbins.min(),xbins.max(),ybins.min(),ybins.max()])

plt.colorbar()

fig.set_size_inches(30, 20)
plt.savefig(sys.argv[1], bbox_inches='tight')
</code></pre>

<p>And here is what I obtain:</p>

<p><a href="https://i.stack.imgur.com/QkARi.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QkARi.png" alt="final graph"></a></p>

<p>That's almost what I want. I would like the first level (0-15 on the color bar), which appears in the darkest purple, to appears white on the graph.</p>

<p>Can it be done ?</p>