title: How to fill the textbox background color using Python-pptx?
body: <p>I am using Python-pptx to create ppt, i want to fill the textbox background with other color.</p>
  <pre><code>from pptx import Presentation
  from pptx.util import Inches, Pt
  from datetime import datetime
  from pptx.dml.color import RGBColor
  from pptx.enum.text import PP_ALIGN
  
  prs = Presentation()
  prs.slide_width = Inches(16)
  prs.slide_height = Inches(9)
  blank_slide_layout = prs.slide_layouts[6]
  slide = prs.slides.add_slide(blank_slide_layout)
  
  slide_layout = prs.slide_layouts[5]
  slide2 = prs.slides.add_slide(slide_layout)
  
  title_textbox = slide.shapes.add_textbox(Inches(5), Inches(0.4), Inches(6), Inches(0.6))
  title = title_textbox.text_frame
  
  pic = slide.shapes.add_picture('image_name.jpg', Inches(3.8), Inches(1.3), Inches(8.5), Inches(6))
  
  subtitle_textbox = slide.shapes.add_textbox(Inches(5), Inches(7.5), Inches(6), Inches(1))
  subtitle = subtitle_textbox.text_frame
  </code></pre>