By default, will add travel events to a new sub calendar called "". 

To change the display colour of these events in Google Calendar:

  1. Open your Google Calendar 
  2. Navigate to the left menu and click the three dots icon next to your sub calendar
  3. Select the desired colour from the menu

You may also be able to change the colour of your travel events in your Apple Calendar or other client that you use.

Step 1:

Open your Google Calendar 

Step 2:

Step 3: