If you wish to delete an identifier from the active calendar data this can be done by clicking on the "Active Schedule" link, which brings up the active calendar being used by the Portal.
In this view, colors that have yet to be published will be more pronounced and include the time of day they will be published. Whereas, colors that have already been published to the public are more faded and include no publish time. You cannot delete a color that has already been published.
To delete a future color, from the Active Schedule calendar view you simply click on the color you wish to delete. This will present you with a dialog box confirming the action and, once confirmed, the color will be removed.