Right now, colors for events in the Posterboard display for a calendar have no rule of precedence.
The only precedence I see is the alphabetical order of categories. Soooo, any events with, let's say, a category at the top of the list will show that particular category's color...Not good.
Right now and for the longest time, I've had calendars filled with events mostly with the same color. Why? Because most of them share a category that's at the top of the list.
It'd REALLY be nice if we could choose 'Primary' categories...so's to decide which category takes precedence over the others...so that their respective color will show in the Posterboard view.