title: Assign random color to matplotlib graph
body: <p>I am trying to plot some polygons in matplotlib, and I've been able to use pre-defined HTML colors, but I would like to use random RGB tuples. However, I can't figure it out. </p>
  
  <p>Here's the code I've been trying:</p>
  
  <pre><code>&gt;&gt;&gt; import matplotlib
  &gt;&gt;&gt; matplotlib.use('agg')
  &gt;&gt;&gt; import matplotlib.pyplot as plt
  &gt;&gt;&gt; import random
  &gt;&gt;&gt; fig, ax = plt.subplots()
  &gt;&gt;&gt; ax.plot([1,2,3], [4,5,6], (.4, .5, .6))
  </code></pre>
  
  <p>And I get this error: <code>raise ValueError('third arg must be a format string')</code></p>
  
  <p>What I would like to do eventually, is to do this:</p>
  
  <pre><code>&gt;&gt;&gt; import matplotlib
  &gt;&gt;&gt; import random
  &gt;&gt;&gt; matplotlib.use('agg')
  &gt;&gt;&gt; import matplotlib.pyplot as plt
  &gt;&gt;&gt; import random
  &gt;&gt;&gt; fig, ax = plt.subplots()
  &gt;&gt;&gt; ax.plot([1,2,3], [4,5,6], (random.random(), random.random(), random.random()))
  </code></pre>
  
  <p>Can someone help me out? Thanks</p>