I really wouldn't suggest buying a used water cooling kit online, mostly because you don't know how well it was taken care of, and if they did anything to help with the mixed metals that are in the water cooling systems. In one of my builds a customer bought a water block online used and it had some discolor to the metal inside of the block. For the most part when you buy a water cooling kit make sure that it comes with a piece of silver in the res, normally it will just be a little piece of metal standing up in the middle, but that helps with the mixing of metals so you don't get weird gunk build up in your system. and it also helps by preventing discolor. The other thing that you will want to consider with colored tubing is the fact that leaks can be harder to spot, because when the water leaks out it will sit around the compression fitting or barb fitting for a while before it drops and you won't be able to see it. I run all of my systems for about 30 minutes for leak tests, but for someone just starting I would recommend 12-24 hours. Watch it carefully for about the first 10 minutes and then check back every 30 minutes after that. You also will want to use a dedicated power supply when you first fill your loop, preferably one that has an on off switch, while you do that disconnect the 24 pin from the motherboard if you can access it after your loop is installed while you fill it. If I am able to reach it I will disconnect the 8 pin from the cpu, as well as the cmos battery, because that also puts out a little bit of power.