title: XlsxWriter: add color to cells
body: <p>I try to write dataframe to xlsx and give color to that.
  I use</p>
  
  <pre><code>worksheet.conditional_format('A1:C1', {'type': '3_color_scale'})
  </code></pre>
  
  <p>But it's not give color to cell. And I want to one color to this cells.
  I saw <code>cell_format.set_font_color('#FF0000')</code>
  but there is don't specify number of cells</p>
  
  <pre><code>sex = pd.concat([df2[["All"]],df3], axis=1)
  excel_file = 'example.xlsx'
  sheet_name = 'Sheet1'
  
  writer = pd.ExcelWriter(excel_file, engine='xlsxwriter')
  sex.to_excel(writer, sheet_name=sheet_name, startrow=1)
  workbook = writer.book
  worksheet = writer.sheets[sheet_name]
  
  format = workbook.add_format()
  
  format.set_pattern(1)
  format.set_bg_color('gray')
  worksheet.write('A1:C1', 'Ray', format)
  
  writer.save()
  </code></pre>
  
  <p>I need to give color to <code>A1:C1</code>, but I should give <code>name</code> to cell. How can I paint several cells of my df?</p>