title: backcolor of readonly richtextbox
body: <p>I have a winforms app with a series of textboxes and one rich textbox. Upon a button click I would like to set all the fields to being readonly. The only issue with this is that the background color of a readonly richtextbox is white as opposed to the grey used by the textboxes. </p>
  
  <p>I have tried setting the backcolor property of the richtextbox to being Color.LightGrey but this is not the same grey used by the textboxes. I have also tried setting the back color to being the backcolor of one of the readonly textboxes but this does not work either. </p>
  
  <p>My question is really is what is the best way to get a readonly rich text box that looks like a readonly text box?</p>
  
  <p>Many thanks</p>