Have always been earth-colours especially brown-tones on the one hand and blues with a focus on navy on the other.
There is a fun theory invented by some eccentric nobleman of my acqaintance that draws parallels between the prominent forces of the military (Army, Navy, Air Force) and the elements*, and clothes. According to him all those components ought to be combined in the right proportion in order to make one a dashingly well-dressed gentleman (or Ehrenmann or gentilhomme, depending on where you live).
Basically the theory says that the Army stands for the element of earth and all its colours. Its contribution to good clothes is structure and material (fabric, weave), its overall feel and comfort. Then, there is the Air Force: element 'air' of course; its characteristic is not colour-it uses them all- but rather the cut, the sharpness, the lines of the clothes. And finally we'd have the Navy: the element of water, that contributes elegance and roundness and binds all the other characteristics together…furthermore there was also fire which is supposed to be artillery but it would be a bit too much fuss to explain it thoroughly in this short space: it adds creative splashes of colour here and there (ties, socks, cufflinks, buttonholes, pocket squares [least of which I personally hardly use at all] ) and is also quite important to women (paradoxically – or rather: conclusively- so, for Freudians); anyway, it seemed to be a pretty crazy theory.
* confer the teachings of the philosopher Empedocles there who supposes 4 basic elements: earth, fire, water, air!