The colour of a Caltrics Internet Calendar in Google Calendar is initially determined by Google. However, this is something that is really easy to change.
To change the colour of your Caltrics internet calendar in Google Calendar, do as follows:
Open Google Calendar and in the Main Menu (click the ‘hamburger’ icon, if not visible) on the left hand side, under ‘Other calendars’, you will see ‘Caltrics’ listed.
Mouse over Caltrics and to the right, you will see 3 vertical dots, ‘Options for Caltrics’, click on this and then select the colour you want. The Google calendar display will be updated immediately.