Dictionary

red band en · NOUN · etymology 1

From the red bands worn on their arms.

(UK) A trusty; a trusted prisoner given special privileges.
- It was an extension of the American Trusty system, as was the appointment of other selected prisoners to be 'Red Bands'. 1967, Harley Cronin, The Screw Turns, page 51:
- A red band was a trusty prisoner who could go anywhere in the prison. His job was taking mail to the main office and delivering any other messages for the screws or staff. Red bands had a bad name amongst the rest of the prisoners. 2012, Charlie Seiga, Killer, page 75:

Spelling	Features	Labels	Source
red bands	Number=Plur		lexicographic

From the red color of the horizontal bar on the cinematic rating screen at the start of the show.