You can make each calendar a different color by applying a category to all the calendar items.
- Open the first shared calendar and then close your personal calendar.
- Select the Organise tab.
- Switch from Grid to List view by clicking on the List icon.
- Click on the first calendar item row to select it.
- Select Edit | Select All.
- Click on the Categorise icon and select a color, name the calendar, and click OK.
- Click the Organise tab and switch List to Grid.
- Do this with each shared calendar.
- You can now view them all together differentiated by colour.