OAuth2

When syncing via OAuth2, CalenGoo can download the colors from Google Calendar, i.e. it can download the calendar colors and the colors of individual events. Additionally you can turn "Settings", "Display and Use", "All", "Expert/Maintenance" (at the end of the list), "Use OAuth2 font colors" on to also use the font colors that you specified in Google Calendar.

To configure the font color in Google Calendar, just click the button to the right of the calendar's name and choose "Choose custom color":

There you can choose a custom color for the calendar and you can also choose between black and white for the font: