In the Canadian Armed Forces, the purple trades are occupations and careers that are not strongly linked to one of the three major 'environments' or 'elements': sea, land, or air.
Purple trades include – but are not limited to – those associated with logistics and administration, medicine, justice, chaplains, and military police.
[2] In the 1980s, the Canadian Forces – while remaining fully unified – assigned each of its members to one of three 'environments': sea, land, or air.
Individuals whose trades weren't directly and obviously linked to specific environments – doctors, purchasing clerks, military police, etc.
A fighter aircraft wing might end up with a medic in navy black and a procurement clerk in army green.