Another source suggests it was simply because the Romanian army wasn't able to standardise colouring in the various factories until a few years later

As used by US officers for everyday environments

Engraved Buttons

Vintage Militaria / Cold War Issue / Dated 1972

this blazer is issued to Finnish sailors who've passed through training and is worn for ceremonial occasions during the summer months

British Army No. 1 Dress Jacket - Queen's Royal Gurkha Engineers - Medium 170/104 Overtrousers Another source suggests it wasAt a glance 100% Wool Material 2 Front Pockets Button Closure Operational Service Medal for Iraq & Syria w Rosette, HM The Queens Platinum Jubilee Medal, HM The Queens Platinum Jubilee Medal & Army Long Service and Good Conduct Medal Medal Ribbon Bar Engraved Queen's Gurkha Engineer Buttons Queen's Royal Gurkha Engineer Collar Badges Company Sergeant Major's Bullion Thread Rank Patch Shoulder Epaulettes Quality Construction Solid Black Colour Pit to