When you use multiple colors, you need to keep real clear what each color is for, so you and your reader do not get mixed up and confused.
I've gotten myself mixed up when I used multiple colored highlighters to highlight my text books in college.
The errors marked in Red might go to the secretarial / clerical staff who operated the keyboard to check against the original, but most likely end-up on the desk of document's originator to be checked. That might result in a call/email from them to the person checking the document, and perhaps cause a significant delay, especially if there are 'cascading' errors in the remainder of the document.
The changes marked in another colour have more to do with style, grammar etc, so are taken care of quickly.
The originator gets a scan of the marked-up document so they can do better next time - if there is a next time for them.
OBTW - there is a convention for mark-up / proofreaders. http://www.merriam-w...le/proofrea.htm
Edited by Sandy1, 23 April 2015 - 15:29.