If you have upgraded your Outlook to the 2007 version, you will need to perform an upgrade to Color Categories to maintain a consistent look for marking and categorizing your emails. If you don’t, you will have a mixture of bars and squares that make for a confusing Inbox.
1. Right-click the main folder that contains your Inbox, Deleted Items, Sent Items, etc. Select Properties.
2. At the bottom of the Properties window, click the Upgrade to Color Categories button.
3. When asked to confirm the upgrade, click the Yes button. The upgrade may take a little while to complete, but you can continue to use Outlook while it does this.
This will also need to be performed on all Outlook Data Files.
So you have gone from this unattractive combination: