You can edit the color labels only in calendars in your own Exchange
mailbox, a Personal Folders .pst file, or an Exchange public folder where
you have Owner permissions.

Signature
Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> How do I edit labels within Outlook if the 'edit labels' bar is grayed
> out?
> I'm a PA and juggling several calendars, colour coding would be really
> useful
> to me if I could personalise it. The standard options are no use to me.