In the Options → Calendar → Colour Mapping to a Category section:
The colour names ( Purple, Bold Green, Yellow, etc. ) do not match Google’s names for these colours in Coogle Calendar.
I suggest ( at least for Google Calendars ) these names are now changed to the Google names to make things easier for the user.
The name eqivalents are:
Rainlendar == Google
Bold Red == Tomato
Orange == Tangerine
Green == Sage
Turquoise == Peacock
Blue == Lavendar
Gray == Graphite
Red == Flamingo
Yellow == Banana
Bold Green == Basil
Bold Blue == Blueberry
Purple == Grape