See this thread
https://www.britishbadgeforum.com/fo...ghlight=Guards
Dark navy blue is the correct backing colour for parachute wings worn on Foot Guards scarlet Full Dress but officers (may) wear parachute wings with a scarlet backing which are private purchase.
However, there remains a mystery that there is no listing in JSP768 of parachute wings on dark navy blue backing for Foot Guards.
As I posted above, the version for the Life Guards, who wear a scarlet tunic in full dress, might be the answer.
Tim