Can I change the colour of Event Types? eg Public Holidays a different colour to confirmed bookings.

Yes you can.  Navigate to Side Menu > Event Settings > Event Status and create a new status called "Public Holiday" with a relevant colour.  You can then assign that status to an event and it will show on the calendar as a different colour providing your are viewing by Status Colour.   To check or change this, while viewing the calendar, click on the Cog Settings Icon, top right of Calendar and on the first dropdown option choose "Show By Status Colour".  

Please note that the option to view by Status Colour only affects your logon, these are personal settings, so a co-worker will not see the same unless they also choose "Show By Status Colour" also.