title: subplots with plotly express 4
body: <p>I have the following, using plotly express:</p>
  
  <pre><code>fig = px.line(series1, x='timestamp', y='data')
  fig.show()
  </code></pre>
  
  <p>and it works properly.</p>
  
  <p>I want to make multiple plots together, so I did:</p>
  
  <pre><code>fig = make_subplots(rows=2, cols=1)
  
  fig.add_trace(px.line(series1, x='timestamp', y='data'), row=1, col=1)
  fig.add_trace(px.line(series2, x='timestamp', y='data'), row=1, col=1)
  
  fig.add_trace(px.line(series2, x='timestamp', y='data'), row=2, col=1)
  
  fig.show()
  </code></pre>
  
  <p>but I get:</p>
  
  <blockquote>
    <p>Invalid element(s) received for the 'data' property of 
           Invalid elements include: [Figure({
       'data': [{'hoverlabel': {'namelength': 0},</p>
  </blockquote>
  
  <p>although,</p>
  
  <pre><code>fig = make_subplots(rows=1, cols=2)
  
  fig.add_trace(go.Scatter(x=series1['timestamp'], y=series1['data']), row=1, col=1)
  fig.add_trace(go.Scatter(x=series2['timestamp'], y=series2['data']), row=1, col=1)
  fig.add_trace(go.Scatter(x=series2['timestamp'], y=series2['data']), row=1, col=2)
  
  fig.show()
  </code></pre>
  
  <p>will work; so it looks like plotly express doesn't work with subplots.</p>
  
  <p>did I miss anything?</p>
  
  <p>additionally, as a bonus question: I haven't found how I can specify the color for each of the traces.</p>