Green’s Dictionary of Slang

a supervisor, a manager.

1957		J. Greenway ‘Australian Cattle Lingo’ in AS XXXIII:3 167: red light, n. phr. A manager or ranch foreman.
1967		K. Tennant Tell Morning This 205: [K]eeping guard to warn the others when a ‘red light’ in the shape of one of the heads appeared.