Q: Outlook 2011 for Mac "Categorize" Question

I have put my contacts in various categories in Outlook for Mac 2011 -- Manager, Staff, etc -- and have identified those different categories with a color marking that shows in the inbox.  This allows me to quickly gauge an e-mail and who its from.

The question is why does the category and color disappear if the person sending me an e-mail places an attachment to the e-mail?  The same person can send an e-mail without an attachment and the category they are in appears -- once that contact attaches any type of document to the e-mail, their category doesn't show and the color defers to black text.

Help please...it's maddening!

Much Thanks