title: Change color scheme of heatmap in Plotly
body: <p>I wanted to create a heatmap of a probability density matrix using plotly.</p>
  
  <pre><code>import numpy as np
  from plotly.offline import download_plotlyjs, init_notebook_mode, plot
  import plotly.graph_objs as go
  
  probability_matrix = np.loadtxt("/path/to/file")
  trace = go.Heatmap(z = probability_matrix)
  data=[trace]
  plot(data, filename='basic-heatmap')
  </code></pre>
  
  <p>This gives me an image like this:</p>
  
  <p><a href="https://i.stack.imgur.com/T3sho.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T3sho.png" alt="basic-heatmap"></a></p>
  
  <p>But after printing the image on a piece of paper, it looks very dark (color printing) and becomes completely indiscernible after black and white printing. I was wondering if I could change the color range arbitrarily; so that the whole image looks a bit softer or lighter.</p>
  
  <p>For example: 1 could be white and 0 could be very <strong>light</strong> blue or a softer color; so that the whole image looks more lighter after printing on a paper.</p>
  
  <p>Note: not sure if this should be a separate question, since I have asked another question related to plotly <a href="https://stackoverflow.com/questions/50086566/smoothen-heatmap-in-plotly">here</a>.</p>