If you aren't familiar with Traffic Light Protocol, please check this link first:
When you create a new file in Google Drive, you'll see this little banner at the top that says "To comply with policies, fill in missing fields."
If you click the "Fill in required fields" button, you'll see this sidebar for "Labels".
There's a label called Sensitivity, and it wants you to choose a Traffic Light Protocol Option.
Once you choose one, that warning bar will go away.
At the top, you can see by the name of the document how the TLP level is super obvious.
Same down here when we're looking at a list of files, the TLP is super obvious.
This isn't enforced or anything, at least not currently, it's just there to give everyone who can see the document a quick visual indicator of how careful they need to be.