How can I set different colors in the calendar boxes?¶

Colors are set by "metadata" you include on each ride.

On the Ride Summary page, select the "Notes" tab. Enter a ride description, like "Race". GC will parse the notes for key words and color the calendar accordingly to a list.

The calendar color list is located in the ("Options..." on linux, "Preferences" on Mac) dialog, select the preferences menu item
Linux/Windows: Tools->Options...
Mac: Preferences

On the dialog select Settings->"Ride Data"->"Notes Keywords". You'll see a list of keywords that are already there, you can edit the color, insert new keywords, or move things around. Colors are changed by clicking the color box. Keywords, and "related notes keywords" are changed by clicking, and editing directly in the list.

I will say that GC can get confusing when by entering multiple keywords. I think GC will color based on the first keyword encountered in the order of the list, but I have not totally tested that theory yet. I'm also not quite sure the rules for the "related notes keywords", though my experience is it will use the same color for all keywords on the line.