There seems to be so much contradictory information in regards to coolants. Especially when it comes to coloured liquid. I don't know the reasons why but from reading around before building mine, it seemed fesser can break down and clog up your blocks (note I said can not will, some people do seem to be able to use without problems.) Again from reading around Mayhems dye seems to be no problem though some people say it fades. Personally, it was my first loop so to remove all hassle I stuck to some distilled water and just used coloured tubing.
Never had experience with swapping out watercooled components constantly but would expect the the tubing to stretch as it goes over the barbs/compression fittings. Thinking about it you might be able to get away with barbs if they have a lip on the end as a hose clamp would keep it in place. Even then I don't know if its possible, hopefully someone else could answer that who has more experience.
I notice you are modding your 932 case but even then I don't know how easy it would be to fit a 360 and 240 in the case. As I said you could more than likely squeeze a 360, a 120 and another 120 in, though I don't know the route the tubing would take for that. What little I did work out for this set up, the 360 rad fittings would need to be in the drive bay end to give enough room for rad and fan at the rear otherwise it would foul and the 120 in the drive bays the fitting would be at the bottom to avoid the 360. The obvious problem with this would be the amount of tubing and fittings to get together in the small amount of room. All this is, shall I say, conjecture as a triple rad should cool cpu and single gpu loop with no problem. As reference, the super computer built in the other thread is 2 cpus and 2 gpus on a 360 and a 120.