The latest approved patents show full color rear displays that could be integrated on future entry-level and mid-range smartphones form LG and Samsung. Samsung's rear screen patent depicts a display half the size of the main one, while LG would only implement a smaller one above the rear camera. The flagship models would get flexible OLED displays that fold into dual screens.
https://www.notebookcheck.net/Samsung-and-LG-could-add-rear-screens-on-future-smartphones.320284.0.html