Unfortunately, Photo Booth doesn't support Camo yet.

There is a workaround for macOS 10.15 users, which is to right-click on Photo Booth in Applications, and choose "Duplicate", before running the duplicate, which will be named "Photo Booth copy". Camo will appear as an option in Photo Booth's menu once this is done.

Camo supports Photo Booth without this step for users running macOS 12.3 and newer; if you are able to upgrade we would recommend it.