Yellow Means Creepy: The Color-Coded Anti-Harassment System Used by Restaurant Workers.

When a staff member experiences harassment, they report the color — “I have a yellow at table three” — and management is required to respond immediately, no questions asked. With a yellow, the employee could choose to switch tables. Orange means the manager or another server immediately takes over the table. If red is reported, the manager ejects the customer from the restaurant.

Relevant: Gruß aus der Küche (Dossier).