title: Altair: Selecting a color from a Vega color scheme for plot
body: <p>So I know that you can select colors in an Altair plot by setting <code>color='blue'</code> or by specifying a hex code. I was wondering if it's possible to instead use a single color from a Vega color scheme like dark2 or set1 without explicitly specifying its hex code.</p>
  <p>I want it be something like:</p>
  <pre><code>
  color = sample_from_scheme('set1')
  
  alt.Chart(df).mark_circle().encode(
      x='X',
      y='Y',
      color=color
  ).save(
      &quot;image.html&quot;
  )
  </code></pre>