If you want to automatically assign categories to messages, that will need
to be a rule and it would only run while Outlook is open. I'm not sure if
you want to do this.
Either way, once the category is assigned through a rule or if you add it
manually to items, you can then use Automatic Formatting rules to individual
folders' views to color-code the items.
Automatic Formatting is set through the View menu | Current View |
Customize Current View... | Automatic Formatting. Add a rule | Condition...
| Advanced. From here you can create formatting rules based on the
Categories value for each item. Keep in mind the built-in formatting rules
take precedence. For example, if a formatting rule you create colors items
in a certain category yellow - if that item is flagged and that flag is
overdue, the item will be colored red instead of yellow due to the built-in
"Overdue e-mail" rule. As far as I know, you cannot re-order the built-in
formatting rules so your custom rules take precedence, however you can
disable them.
If you have many folders containing mail items for which you want to use
this, you can go to View | Current View | Define Views... and create a view
(or modify/copy-&-modify an existing one) to include these Automatic
Formatting rules. When naming the rule, as long as you set the "Can be used
on" option to "All mail and post folders," you can set this custom view for
each applicable folder rather than re-creating the view for each one.
