Do one of the following:
Note The Flag color option is not available for contacts.
Automatically add a flag using a rule
If you want to run a newly created rule on messages already in the Inbox, select the Run this rule now on messages already in Inbox check box on the last page of the Rules Wizard.
To have this rule apply to all your accounts and each Inbox, select the Create this rule on all accounts check box on the last page of the Rules Wizard.
Automatically remove flags on messages sent to me
To clear all flags, click Any.
If you want to run a newly created rule on messages already in the Inbox, select the Run this rule now on messages already in Inbox check box on the last page of the Rules Wizard.
To have this rule apply to all your accounts and each Inbox select the Create this rule on all accounts check box on the last page of the Rules Wizard.