Some findings,
- These do not appear in the print preview, hence do not appear in any generated pdf file or hard copy print.
- The markings can not be turned off. The only way out is to go to options and change "Page and Column break" color from "automatic" to "white". But be advised that this does not mean that they disappear or these are colorless. So, if the markings overlap some actual text, those texts will have a somewhat worm-eaten appearance.
The above knowledge was partially found at this discussion.