You are using Exchange Server and there are no less the 3 versions of that.
http://office.microsoft.com/en-us/outlook-help/change-the-appearance-of-your-calendar-HA010030976.aspx#BM2 is about changing the color in Outlook 2007 which might work if you were syncing with your desktop but since it's Exchange Server your IT staff should get it fixed by calling all the parties as needed.
When syncing the Gem with our Outlook exchange server, all the items are colored red on the phone. How can we change this color to something lighter so the item can be read? This is not the gmail calendar, but the exchange server Outlook calendar for work.