While the green get-up is a departure from the white shirt, black pants and green jacket of the previous 12 years, changes were necessary for better function, comfort and cost, Mr Devanney said.
The new uniform, which comprises a dark green shirt, white under-shirt and dark green cargo trousers, costs less to produce than the old one.
"We have estimated there will be a saving of about $400,000 over three years, including replacement and roll-out costs. That's a saving of $130 per uniform kit issued to full-time paid staff," he said.
Another benefit is the fact green is the recognised colour associated with medical care. "We definitely won't get confused with other services."
St John's last major overhaul was in 2002, when the most recent look replaced maroon epaulettes, a tie and a jumper.