I use a Samsung mobile phone with Android 5.0. In the phone I us the calendar app DigiCal. The calendars I synchronize with my OS X Server. OS X has version 10.11.3, and the server application 5.0.15. On the server I create some calendars that synchronize fine with the mobile phone. When creating the calendars I also can give them their default colors.
But now the problem. When I create an appointment in the mobile (DigiCal app) the appointment receives the calendar's default color, and so far sop good. But if I change the color to a color other than the calendar's default color, this color will change back to the default color at the next sync time. I have seen in DAVdroid that there is a setting called Manage calendar colors. In this case it doesn't matter if this setting is on or off. The behavior is the same.