You can specify the author name and color that are used when you add comments. If you’re collaborating with others on a presentation, each collaborator can use a different color.
You can change your author name at any time. The new name appears the next time you comment in a presentation; it won’t change the name that appears on comments you made previously.
Choose Keynote > Preferences (from the Keynote menu at the top of your screen).
Click General at the top of the preferences window.
Enter a name in the Author field, then close the preferences window.
Commented text is highlighted with a color associated with the person who made the comment. You can change your assigned color at any time.
Choose View > Comments > Author Color (from the View menu at the top of your screen), then choose a color.
All your comments in the presentation switch to the new color (as long as you haven’t changed your author name).