title: Python: Is it possible to change line color in a plot if exceeds a specific range?
body: <p>Is it possible to change the line color in a plot when values exceeds a certain y value?
  Example:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  a = np.array([1,2,17,20,16,3,5,4])
  plt.plt(a)
  </code></pre>
  
  <p>This one gives the following:
  <img src="https://i.stack.imgur.com/lYW5o.png" alt="enter image description here"></p>
  
  <p>I want to visualise the values that exceeds y=15. Something like the following figure:</p>
  
  <p><img src="https://i.stack.imgur.com/Eicv8.png" alt="enter image description here"></p>
  
  <p>Or something like this(with cycle linestyle):<img src="https://i.stack.imgur.com/monap.png" alt="enter image description here">:</p>
  
  <p>Is it possible? </p>