Mac OS X Mail knows more flag colors than red, and you can supply the flag's names — one for urgent mail, say, and one for personal emails you cherish —, easily grouping certain messages without moving them.
Rename the Message Flags in Mac OS X Mail
To give a new name to one of the colored flags in Mac OS X Mail:
- Make sure the folder list is visible.
- Press Command-Shift-M if it is not or select View | Show Mailbox List from the menu.
- Now make sure REMINDERS are visible.
- Click Show next to REMINDERS in the mailbox list if they are not.
- Make sure Flagged is expanded.
- If you cannot expand Flagged, flag a message in color different from what you've already used.
- Double-click the flag you want to rename.
- Only flags you have used will be visible.
- To edit a new flag, apply it to an un-flagged message.
- Type the desired name for the flag.
- Press Enter.
(Updated July 2011)

