Another idea is to use detachable air lines, male one end female the other, it doesn’t matter about the colour, they will only fit one way 
Have you ever used the clip on electrical leads on a drawbar trailer, they are one piece and quite easy to use.
I’ve seen a connector used on machines, a bit like a scart lead but much bigger, had a nice big un/locking lever, water and dust proof, electrical and air connections all in one, easy to get inside it to repair. Trying to find an example/piccy. On a tractor unit it’d make perfect sense.
MADBAZ:
I’ve seen a connector used on machines, a bit like a scart lead but much bigger, had a nice big un/locking lever, water and dust proof, electrical and air connections all in one, easy to get inside it to repair. Trying to find an example/piccy. On a tractor unit it’d make perfect sense.
I think I know the sort of thing you are on about. They use the same system for quick release front end loaders on tractors.
This would seem to be the way forward 
http://www.jost-world.com/products/information-and-movies/jost-automatic-coupling-system.html?L=1
