Thanks for your reply, please see answers below.
1. Corporate Exchange
2. There is no visible error message.
3. Steps to repro:
On the calendar, right-click on an event. From the context menu, choose "categorize" and click on any color. The context menu is dismissed immediately (with no further mouse click; there's no ok button)
Expected: the event on the calendar should change color immediately. Subsequent check of the context menu shows the color as selected in the list.
Actual: the event shows no color. Subsequent check of context menu shows no color selected in the list.
Anecdotally, my impression over time is that if _I_ created the event, it works. If somebody else created the event, it does not work. I have created a custom color as a test and had the same res