I found a solution that worked for me. Really just stumbled on it and honestly don't understand why it works, but it has for me. I used category colors for Calendar appointments in Outlook to distinguish between personal, business, travel and other appointments. The colors were not displayed in my calendar views, but when I opened up each individual appointment, the color bars were displayed until I closed the appointment.
The solution:
Open up each appointment (choose "series" if it is a recurring appointment). If your color/categroy is displayed already as a bar across the top, then click "Categorize", choose "clear your-color-here", when the color bar has cleared just reselct your color/category and save.
A pain in *** to have to do this for each appoint, or as many of you need to do with contacts, tasks, etc. but it worked for me.
Unfortunately, for new appointments (going forward) it seems that the category can only be added while the appointment is fully open (no quick right click) Though I did find a few items that could be right clicked, I could not figure out what made them special.
Maybe this approach will help get someone who knows a lot more about Outlook and software in general to identify a better path, but in the meantime, this has worked for me.