Could the use of flashes be related to the RAF hat bands for "Boy Entrant" /Apprentice training in the Royal Air Force ?
"The only distinction from the regular service uniform that was worn, was the use of coloured on chequered hat-bands around SD cap to indicate which subject the boy was studying.
These chequered hat-bands were very distinctive with a wide variety of colour combinations: brown/white – Telegraphists, red/black – Radio & Radar ,red/yellow (blood & custard) – Airframes. Other trades had green/blue,yellow/orange, green/yellow, red/yellow etc"
History of the Boy Entrants
http://www.49th2sqn.org/?page_id=762