I just shared a calendar that I organized for a conference and the category colors I used are not visible to those I have shared the calendar with. Is there a fix for this?

Running MS Outlook 2010 on a Windows 7- x64 machine.
After sharing a calander, some poeple are able to see the color coded schedule and other cannot.

Tried recreating calendar & re-permissioning, but still unable to view color.

Any ideas or tips?

-israel