How do I assign a color to one of my rooms?
When you are on the Calendar, click on "My places" and then on the room concerned.
A window appears on the right. Click on "Modify the place" at the bottom of this window, under the Google Map. Then combine your event with the color you want!
When you indicate that your room is unavailable for a given period, it will be this color that will appear on your Calendar (here the red color was selected).