The simple stuff can drive someone NUTS.

I realize this can be done by track changes and other means, but I want to do something very simple and can't find the solution. In the horse & buggy days of WordPerfect and so on this could be done, but I can't find a solution anywhere:

Suppose I have a document in black font sent by someone who doesn't understand track changes or comment boxes or highlighter, etc. I want to add some comments in red font so they stand out for this recipient when I send it to him. Of course I can type my comments in and change them to red, but that gets laborious. There HAS to be a setting I can use so that just newly inserted text is red and the existing text stays, black. Right???