title: how can i color specific pixels in matplotlib imshow?
body: <p>I am plotting a <code>numpy</code> matrix with <code>imshow</code> and nearest neighbor interpolation in blue scale.</p>
  
  <p>How can i color specific pixels in the plot so that they would be, say red?</p>
  
  <pre><code>pyplot.imshow(matrix, interpolation='nearest',cmap = cm.Blues)
  pyplot.show()
  </code></pre>