I once was demonstrating some VR hardware to a class. They were too many to go all at once so I split them into three groups and decreed:
“You are group 1, you are group B, and you are group Red.”
When I had ran the demo for the first group I yelled:
“OK, time for group B!”
They stepped up and primly declared:
“We are group 2.”
Conventions are practical, but they’re not mandatory.